Natural Selection

[KT45]

I’ve been reading Richard Dawkins book “The Selfish Gene” and I’m starting to learn more and more about natural selection. Thankfully while in school I was lucky enough to have a teacher that wasn’t religious and tried to teach the subject. Unfortunately I didn’t pay attention as much either because of my Christian background or just because of plain boredom. Before I ask my questions I want to see if I even have a decent grasp of natural selection by giving an example I learned a long time ago in high school.

 

Natural Selection Example: A group of giraffes typically eat from the trees to eat the leaves. One giraffe has a child that has a mutation giving him a slightly longer neck than the others. This giraffe ends up healthier than the other giraffes. It more than likely is able to outrun predators more efficiently than his peers due to his diet. It is also more likely to find a mate to reproduce. After a while that giraffes has offspring that have the same “slightly longer neck” gene as the parent. These giraffes over populate the others. This continues until another giraffe has a mutation that creates a “long neck” gene making him more successful. Over time the giraffes either die out because of lack of food or because finding a mate was too difficult. You now end up having a new species of giraffe that is different from the older species.

 

 

Is this close to being correct? I hope so or the following questions are just pointless. Well anyway here goes.

 

Why did natural selection choose the following traits that are listed below (if answered on another source please link it or offer a book recommendation)

 

Being able to see color? – Why would natural selection prefer humans with colored vision over those without it? There are plenty of species that do very well without the ability to see color so I just don’t see how this genetic mutation could prevail over colorblindness.

 

Standing Up-right - Why would humans evolve to stand up-right? Does it make us faster than animals who can’t (like chimps)

 

Hair only on head – Why have our genes gone for the none hairy look but only keeps hair on head. I believe that their our very few animals with genes that limit hair growth so why would natural selection cause us not to have them.

 

Skin Color – Black, white, yellow, brown, red. We all have different skin shades because of the melon (spelling?) in our skin. My question is if this is a form of evolution/natural selection or some other reason? If it’s merely adaptation what is the difference between adaptation and natural selection?

 

Homosexuality – Why would this evolve? Is this genetic?

 

Asexual vs. Sexual reproduction – I guess that at one point an asexual creature somehow had a genetic mutation that required it to have the genes of a creature of the same species. It’s kinda hard to see how this exactly happened?

 

Monogamy – Like in swans. To me it seems like having many partners will increase the chances of your genes surviving rather than only having one partner. Most creatures are non-monogamous and do fine so why did we evolve that way?

 

When a doctor says that a person has a genetic defect are they really saying he has a mutation ?(just not one that is considered beneficial). Would a mutation be similar to a child being born with more than one finger?

 

Claws/nails- Most creatures whether they live in trees or live on the ground have claws. Why don’t primates?

 

Tails – They seem pointless. Why don’t we have one but other animals do?

[Entgegen]

Your example of natural selection is pretty much how it goes, only it's not that the shorter-necked giraffes "die out" because of lack of food/mate, their numbers just become proportionately smaller because longer-necked giraffes are able to produce more offspring and/or produce offspring more quickly. A there is never a population with 100% of all individuals sharing identical traits...just "long-neckness" is the most common, but there will always be those with slightly shorter and slightly longer necks. Anyway, on to your questions:

 

Color vision: Many primates (including chimps, our closest cousin) have color vision, humans included. But think of it this way: although many animals do just fine without color vision (as we know it), how would they do if they did have color vision? The appearance of color vision happened through chance, not because natural selection was pushing colorless vision toward it. So, once color vision came about, it allowed those endowed with it to distinguish more things, say, colored fruit standing out against a differently-colored background, and things of that nature. Color vision gave those with it an advantage (supposedly, otherwise color vision probably wouldn't have been retained), and therefore had a positive impact on how it lived, and therefore allowed it to propogate its genes that much better/efficiently.

 

I'll write more on your other questions, but I have to go to class now. Hope this has helped so far.

 

P.S. Dawkins' book The Blind Watchmaker is exclusively about the workings of natural selection. Check it out.

[Reverend AtheiStar]

Tails – They seem pointless. Why don’t we have one but other animals do?

 

Some humans do! Check this out:

 

http://www.reverendatheistar.com/macroevolution2.htm

 

Example 2: Newborn babies born with tails

 

Primarily due to intense medical interest, humans are one of the best characterized species and many developmental anomalies are known. There are several human atavisms that reflect our common genetic heritage with other mammals. One of the most striking is the existence of the rare "true human tail" (also variously known as "coccygeal process," "coccygeal projection," "caudal appendage," and "vestigial tail"). More than 100 cases of human tails have been reported in the medical literature. Less than one third of the well-documented cases are what are medically known as "pseudo-tails" (Dao and Netsky 1984; Dubrow et al. 1988). Pseudo-tails are not true tails; they are simply lesions of various types coincidentally found in the caudal region of newborns, often associated with the spinal column, coccyx, and various malformations.

 

In contrast, the true atavistic tail of humans results from incomplete regression of the most distal end of the normal embryonic tail found in the developing human fetus (see Figure 2.4.1 and the discussion below on the development of the normal human embryonic tail; Belzberg et al. 1991; Dao and Netsky 1984; Grange et al. 2001; Keith 1921). Though formally a malformation, the true human tail is usually benign in nature (Dubrow et al. 1988; Spiegelmann et al. 1985). The true human tail is characterized by a complex arrangement of adipose and connective tissue, central bundles of longitudinally arranged striated muscle in the core, blood vessels, nerve fibres, nerve ganglion cells, and specialized pressure sensing nerve organs (Vater-Pacini corpuscles). It is covered by normal skin, replete with hair follicles, sweat glands, and sebaceous glands (Dao and Netsky 1984; Dubrow et al. 1988; Spiegelmann et al. 1985). True human tails range in length from about one inch to over 5 inches long (on a newborn baby), and they can move via voluntary striped muscle contractions in response to various emotional states (Baruchin et al. 1983; Dao and Netsky 1984; Harrison 1901; Keith 1921; Lundberg et al. 1962).

 

Although human tails usually lack skeletal structures (some medical articles have claimed that true tails never have vertebrae), several human tails have also been found with cartilage and up to five, well-developed, articulating vertebrae (see Figure 2.2.2; Bar-Maor et al. 1980; Dao and Netsky 1984; Fara 1977; Sugumata et al. 1988). However, caudal vertebrae are not a necessary component of mammalian tails. Contrary to what is frequently reported in the medical literature, there is at least one known example of a primate tail that lacks vertebrae, as found in the rudimentary two-inch-long tail of Macaca sylvanus (the "Barbary ape") (Hill 1974, p. 616; Hooten 1947, p. 23).

 

True human tails are rarely inherited, though several familial cases are known (Dao and Netsky 1984; Ikpeze and Onuigbo 1999; Touraine 1955). In one case the tail has been inherited through at least three generations of females (Standfast 1992).

 

 

Figure 2.2.2. X-ray image of an atavistic tail found in a six-year old girl. A radiogram of the sacral region of a six-year old girl with an atavistic tail. The tail was perfectly midline and protruded form the lower back as a soft appendage. The five normal sacral vertebrae are indicated in light blue and numbered; the three coccygeal tail vertebrae are indicated in light yellow. The entire coccyx (usually three or four tiny fused vertebrae) is normally the same size as the fifth sacral vertebrae. In this same study, the surgeons reported two other cases of an atavistic human tail, one with three tail vertebrae, one with five. All were benign, and only one was surgically "corrected" for cosmetic reasons (image reproduced from Bar-Maor et al. 1980, Figure 3.)

 

As with other atavistic structures, human tails are most likely the result of either a somatic mutation, a germline mutation, or an environmental influence that reactivates an underlying developmental pathway which has been retained, if only partially, in the human genome (Dao and Netsky 1984; Hall 1984; Hall 1995). In fact, the genes that control the development of tails in mice and other vertebrates have been identified (the Wnt-3a and Cdx1 genes; Greco et al. 1996; Prinos et al. 2001; Schubert et al. 2001; Shum et al. 1999; Takada et al. 1994). As predicted by common descent from the atavistic evidence, these tail genes have also been discovered in the human genome (Katoh 2002; Roelink et al. 1993). As discussed below in detail, the development of the normal human tail in the early embryo has been investigated extensively, and apoptosis (programmed cell death) plays a significant role in removing the tail of a human embryo after it has formed. It is now known that down-regulation of the Wnt-3a gene induces apoptosis of tail cells during mouse development (Greco et al. 1996; Shum et al. 1999; Takada et al. 1994), and similar effects are observed in humans (Chan et al. 2002). Additionally, researchers have identified a mutant mouse that does not develop a tail, and this phenotype is due to a regulatory mutation that decreases the Wnt-3a gene dosage (Greco et al. 1996; Gruneberg and Wickramaratne 1974; Heston 1951). Thus, current evidence indicates that the genetic cause of tail loss in the evolution of apes was likely a simple regulatory mutation(s) that slightly decreased Wnt-3a gene dosage. Conversely, a mutation or environmental factor that increased dosage of the Wnt-3a gene would reduce apoptosis of the human tail during development and would result in its retention, as an atavism, in a newborn.

 

Criticisms:

 

The existence of true human tails is unfortunately quite shocking for many religiously motivated anti-evolutionists, such as Duane Gish, who has written an often-quoted article entitled "Evolution and the human tail" (Gish 1983; see also Menton 1994; ReMine 1982). Solely based on the particulars of a single case study (Ledley 1982), these authors have erroneously concluded that atavistic human tails are "nothing more than anomalous malformations not traceable to any imaginary ancestral state" (Gish 1983). However, their arguments are clearly directed against pseudo-tails, not true tails. Gish claims these structures are not true tails for several reasons: (1) they lack vertebrae, (2) they are not inherited, and (3) the resemblance to tails is "highly superficial" and simply an "anomalous malformation." Menton further claims that (4) all true tails have muscles and can move, whereas human tails cannot. Each of these arguments are factually false, as explained above and as well-documented in the medical literature. Vertebrae and cartilage have occasionally been found in human tails. However, contrary to the claims of Gish, Menton, and ReMine, vertebrae are not a requirement for tails. M. sylvanus is a prime example of a primate whose fleshy tail lacks vertebrae (Hill 1974, p. 616; Hooten 1947, p. 23). Several cases are known where human tails have been inherited. Furthermore, we now know the genes responsible for the development of tails in mammals, and all humans have them. Inheritance of the tail structure per se is unnecessary since the developmental system has been inherited but is normally inactivated in humans. The "resemblance" to non-human tails is far from superficial, since all true human tails are complex structures composed of symmetrical layers of voluntary muscle, blood vessels, specialized nerves and sensing organs, and they can indeed move and contract.

 

For the skeptical reader, probably the best evidence that these structures are true tails is visual inspection. Photographic images of a newborn's atavistic tail can be found at the University of Iowa's Virtual Hospital site, complete with the voluntary contractory movement of the tail documented.

[Entgegen]

Before I start again, it's good to reiterate the sort of "selection thinking" you have to do when reasoning through these things. Remember that natural selection is a passive (yet powerful!) force; it cannot push or pull attributes or develop them, but it does guide those that are already there (and new ones that come about through mutation), for better or for worse. It depends on the environmental pressures. Since environments change, one attribute that may be useful at one point in time may not be in at another time.

 

Walking Upright: This one is pretty speculative (as if any of these explanations aren't...), but a big hypothesis for the development of bipedal locomotion is that it frees up the hands to do things. While chimps and other "higher" primates are normally quadrapedal, they have been known stand upright and walk on their hind legs, particularly when they are carrying something. Another reason floating around out in the hypothetical biological ether is that it decreases the surface area exposed to the sun, keeping us cooler, since the general scientific consensus is that humans evolved in Africa. Also, think about this: chimps are hairy all over, with more of their bodies exposed to the sun, while humans' hair is more confined to the top of the head (though I know of many humans who are notable exceptions...), which is what is exposed to the sun (technically the shoulders are too, but hey, it's speculation). I personally feel the freeing of the hands thing is the biggie, and surface area exposure came as a later benefit. But if your hands are freed to do more, that obviously can be seen as a selective advantage to help live a better life.

 

Hairy Head: I sorta' touched on this in the response above (I neglected to notice this particular question to begin with). But pretty much, if we're upright, we don't need hair all over us to protect from the sun, just the parts of us exposed. It's just more economical to not have to produce so much hair. Energy is needed for everything going on in the body, growing hair included. If that energy can be freed to go towards some other process in the body, I see no reason why it wouldn't (given enough time, of course).

 

Skin Color: Many say that skin color is a result of evolution/natural selection, which is sort of the current thinking on why "white" people lack the pigment that darker-skinned people have. Current thinking is that we (humans) evolved in Africa, where it is very sunny. In response to sunlight, our body produces melanin, the skin pigment. This skin pigment offers protection from the sun, hence people from mainly equatorial regions of the world (Africa, Latin America, Australia [Aboriginals], etc.) have darker skin than those from higher/lower latitudes. Our ancestors were all dark skinned, but after moving out of Africa and populating other areas of the globe that recieve less sunlight, our skin began to lighten (perhapse because it was more economical not to produce so much melanin, like body hair).

 

Homosexuality: This one is pretty speculative also. I have heard that brain scans of homosexual individuals reveal that their brain patterns resemble those of the opposite sex. Whether this comes about because of the way they're brought up or if it's genetics, I'm not sure what the scientific "consensus" is on this. I personally think that since their brains seem to be wired somewhat differently, it has a lot to do with genetics. Also, I've heard of a case (I'm not sure whether this is an urban myth or not, so feel free to take this with a grain of salt) where a baby was being circumsized, and the doctor nipped off a little too much. He suggested to the parents that they just remove the rest and raise it as a girl. All was fine until years later the "girl" found "her"self attracted to other girls, at which point "she" tried to kill herself, and the parents confessed. Again, the validity of this story is questionable at best. But if this is true, then biology would seem to take precedence over nurturing, further strengthening the supposition that homosexuality (and heterosexuality, for that matter) are genetic. As to why this hasn't been a "lost" trait, one that wouldn't propogate itself (provided the homosexual was faithfully homosexual), some have suggested that homosexual acts readily seen in nature (there was an article about it in Seed Magazine this past summer) can strengthen the bonds between males of a group. And generally (I would assume) in this case, these animals are not faithfully homosexual, and thus passing on the trait for homosexual behavior.

 

Asexual Reproduction: The biggest difference between sexual and asexual reproduction is that it introduces genetic variation. Genetic variation is a big driver for evolution, as there's new genetic material always being introduced, which is what happens in sexual reproduction. The product of asexual reproduction is simply a clone of the organism undergoing asexual reproduction. But as for how it came about, there are sort of instances even in bacteria of "sexual" (sexual meaning simply transfer of genetic material) acts going on, such as plasmid transfer. A plasmid is a little circular strand of DNA that is sometimes transfered from bacteria to bacteria, and as a consequence, you get horizontal transfer (vertical transfer is through the act of reproduction) of DNA that can lead to things like antibacterial resistance. So the transfer of genetic material between individuals can lead to genetic variation, which in turn can lead to greater "fitness". It seems almost inevitable that early organisms would begin to reproduce in a way that would lead to greater genetic variation.

 

Monogamy: You are correct in assuming that greater numbers of mates would increase your chances of passing on your genes. As for swans, I'm not sure. There's probably something about being monogamous for swans that provides a benefit that can override the benefit of having more mates...perhaps a swan is taking a safe way and insuring that it will always have a receptive mate with which it can have offspring. When there's slim pickin's as far as mates go, swans may have an advantage in that they'll always have someone to be with. But I guess it depends on what works in your environment and what doesn't: some places may foster sexual promiscuity more than others, and the organisms in that environment will probably act accordingly. As for humans, I'm not sure we really evolved to become monogamous...it seems more of a cultural byproduct. But as far as from an evolutionary standpoint, it may be like the swan: insurance.

 

Genetic Defects: Yes, generally genetic defects are mutations. Take sickle-cell anemia. It is a result of a point mutation (a single base-pair shift) in a gene that encodes beta-hemoglobin (however, this mutation has a selective advantage when dealing with malaria, which is why many people with sickle-cell anemia have close genetic ties to people in areas where malaria is common). Polydactyly (more than normal fingers/toes) is a result of a mutation in Hox genes, or, more specifically, the DNA sequences that regulate the Hox genes.

 

Claws: Primates (including humans) do have claws: they're nails. They're all the same sort of thing, in the same place on the body, and made out of the same substance (keratin; it's also the stuff hair and horns in animals are made of)

 

Tails: Tails are far from pointless. Many animals use them for balance (particularly tree-dwelling animals, and cheetahs as well as other runners), locomotion (fish, whales/porpuses, bevers), sheep keep a fat reserve in their tails, hoofed animals use them as a fly whisk, wolves and other animals use them for signaling, spider monkeys use them as a sort of fifth arm. I really have no explanation as to why some animals (like hamsters, bears, bats, moles, hedgehogs, koalas, sloths, etc.) lost their tails, but perhaps human ancestors lost theirs because it was a neusance while walking upright. But that's be best I have for that.

 

Anyway, I hope this helped out some, and I enjoyed writing it (it took a while though), and ask if there's something else I can help with. Also, anyone feel free to comment/critique/make this better/clarify things about this.

[KT45]

Entgegen thanks for your post. It's helping me better comprehend a subject I should have learned in the first place

 

Your example of natural selection is pretty much how it goes, only it's not that the shorter-necked giraffes "die out" because of lack of food/mate, their numbers just become proportionately smaller because longer-necked giraffes are able to produce more offspring and/or produce offspring more quickly.

Can you tell me why they would be able to produce more offspring quickly?

 

P.S. Dawkins' book The Blind Watchmaker is exclusively about the workings of natural selection. Check it out.

Thanks will do!

 

Tails – They seem pointless. Why don’t we have one but other animals do?

 

Some humans do! Check this out:

 

http://www.reverendatheistar.com/macroevolution2.htm

it's amazing how some genes can stay alive for so long. In the book "the selfish gene" it talks about how genes are the ones that control us like preprogrammed robots to keep themselves alive. I just find it incredible how a normally non-existant gene, like one that gives human tails, can still survive for so long!!!

[Entgegen]

Can you tell me why they would be able to produce more offspring quickly?

 

Well, assuming that longer necks lead to greater health benefits, one could imagine perhaps females would have quicker turn-around periods (less of a time lag between subsequent pregnancies), and perhaps males could have more energy to expend on being more promiscuous. This is all highly speculative of course, but you get the idea of how natural selection is more than just simply "survival of the fittest" and can enter in many facets of lives of organisms. Hope this helps!

[Dhampir]

I have red-green colorblindness. I read up on it, and there's a hypothesis that states that as we be become less reliant on color to discern the dangers of our environment, we start to lose it.

[Skankboy]

Just a quick note on the "hair on head" question. We actually do have just as much hair per square inch on most of our body as primates. Our's is just thinner and lighter (the notable exception being Robin Williams). The savannah theory believes this was a response to our biped locomotion combined with savannah heat. Makes us less of a target for the sun and allows for more rapid cooling.

[Darkside]

I have red-green colorblindness. I read up on it, and there's a hypothesis that states that as we be become less reliant on color to discern the dangers of our environment, we start to lose it.

 

That would make sense. I doubt your colorblindness will affect your ability to mate, so the gene will be passed on, whereas "in the wild" this could be a significant handicap that might cause you to die before passing the gene along, so the gene would die out.

 

The notion of how civilization will affect evolution is an interesting one. Beneficial mutations won't necessarily be passed on any more readily than deleterious ones, so there's probably no tendancy to evolve as a species; there may even be a tendancy to go the opposite way.

[Callyn]

Natural Selection Example: A group of giraffes typically eat from the trees to eat the leaves. One giraffe has a child that has a mutation giving him a slightly longer neck than the others. This giraffe ends up healthier than the other giraffes. It more than likely is able to outrun predators more efficiently than his peers due to his diet. It is also more likely to find a mate to reproduce. After a while that giraffes has offspring that have the same “slightly longer neck” gene as the parent. These giraffes over populate the others. This continues until another giraffe has a mutation that creates a “long neck” gene making him more successful. Over time the giraffes either die out because of lack of food or because finding a mate was too difficult. You now end up having a new species of giraffe that is different from the older species.

It probably wouldn't happen like that. The giraffe with the slightly longer neck wouldn't really reach any better food than the other giraffes because there's no selective pressure. Long necks likely evolved long ago when lowlying bushes were dying out in Africa. Also, evolution is not drected, only populations of animals can evolve and it doesn't mean that the old species will die out.

 

Being able to see color? – Why would natural selection prefer humans with colored vision over those without it? There are plenty of species that do very well without the ability to see color so I just don’t see how this genetic mutation could prevail over colorblindness.

Most likely it involved distinguishing food. Fruits are brightly-colored for a reason.

 

Standing Up-right - Why would humans evolve to stand up-right? Does it make us faster than animals who can’t (like chimps)

Yes, it does make us faster and it uses less energy. It's much more useful on a savannah (where we evolved) than a quadrupedal configuration using similar limbs. It also allows a wider field of vision in grasslands.

 

Hair only on head – Why have our genes gone for the none hairy look but only keeps hair on head. I believe that their our very few animals with genes that limit hair growth so why would natural selection cause us not to have them.

It helps us cool down and that's likely to be it. However, all mutations need not be beneficial in order to go to the enxt generation (the appendix, for example).

 

Skin Color – Black, white, yellow, brown, red. We all have different skin shades because of the melon (spelling?) in our skin. My question is if this is a form of evolution/natural selection or some other reason? If it’s merely adaptation what is the difference between adaptation and natural selection?

Melanin. More melanin protects from the sun, while less allows more production of vitamin D. Depending on the environment, the more useful one prevailed. Adaptation is a art of evolution.

 

Homosexuality – Why would this evolve? Is this genetic?[/qote]

It's not a genetic trait, but it's psychological. The more older brothers a male has, the more likely he is t be homosexual because his mother's immune system has antibodies against the Y chromosome.

 

Asexual vs. Sexual reproduction – I guess that at one point an asexual creature somehow had a genetic mutation that required it to have the genes of a creature of the same species. It’s kinda hard to see how this exactly happened?

It happened so long ago that we do't really know what the mutation was. However, it allows for greater genetic diversity that increases a species likelyhood of survival.

 

Monogamy – Like in swans. To me it seems like having many partners will increase the chances of your genes surviving rather than only having one partner. Most creatures are non-monogamous and do fine so why did we evolve that way?

Monogamy increases the care offspring receive, which in species with few offspring increases the generations chances of survival. However, humans aren't completely monogamous, it's more culture.

 

When a doctor says that a person has a genetic defect are they really saying he has a mutation ?(just not one that is considered beneficial). Would a mutation be similar to a child being born with more than one finger?

A mutation is any change in the genetic code. A defect may not be a new mutation, but it is a difference from the most beneficial arrangement.

 

Claws/nails- Most creatures whether they live in trees or live on the ground have claws. Why don’t primates?

Someone answered this, but we do. fingernails and toenails. They're just not utilized the same way.

 

Tails – They seem pointless. Why don’t we have one but other animals do?

Mainly balance, but other animals have developed them towards other uses. We don't hold our bodies in a way similar to any other creatures, and our most closely-related cousins don't have them either. Why, I'm not sure, but we lost them somewhere along the way.

 

The notion of how civilization will affect evolution is an interesting one. Beneficial mutations won't necessarily be passed on any more readily than deleterious ones, so there's probably no tendancy to evolve as a species; there may even be a tendancy to go the opposite way.

There's no way to go backwards in evolution. Evolving to a simpler form is still evolution. Evolution has no purpose in and of itself.

[Reverend AtheiStar]

it's amazing how some genes can stay alive for so long. In the book "the selfish gene" it talks about how genes are the ones that control us like preprogrammed robots to keep themselves alive. I just find it incredible how a normally non-existant gene, like one that gives human tails, can still survive for so long!!!

 

I don't consider genes alive, themselves. They're just organic code. And there are much more ancient genes that the tail genes -- by far! The Hox genes have been preserved since right around the beginning! Read this:

 

"As explained in Endless Forms Most Beautiful, by U.S. geneticist Sean Carroll, one of the leaders of this new field, immediately there were very exciting discoveries. Darwin himself had always argued that the way of evolution is rarely to build the entirely new, but to take the already existing and modify and reuse. The forelimb of vertebrates is a classic example. Don't build a whole new structure for flying. Take what you have -- something used for walking and grasping -- and shape it accordingly.

 

What no one realized is the extent to which this would be going on at the genetic level. Who would dream that there could be something significantly in common between humans and the little fruit fly, Drosophila? But it turns out that there is. Basically, what we now know is that organisms are built on a modular fashion. It is not a question of everything being done at once. Rather, bits and pieces are built, and if you want something more, then you repeat one of the pieces that you have and then modify it. Or you drop one piece and add another kind of piece and so forth. Snakes are obviously built this way -- think of all of those vertebrae -- but the same is true of other organisms. Start with a pair of legs, double them, turn one set into wings -- good idea -- get another set, and turn those into wings as well. And so it goes.

 

But how does it go? It turns out that the answer is at the level of the genes, but not just any genes. Some genes produce substances (proteins) that do not make things, but control the making of things by other genes. They turn on (or off) the DNA. This is the secret to repeating things -- double your DNA and your switches -- and to transforming things -- alter the order of switches or their operating, and you have your desired end product. It is these controlling genes -- what Carroll calls the "genetic toolkit" -- that are the secret to building an organism or of transforming one organism into another kind of organism.

 

What was totally unexpected and incredibly exciting is that these switch genes are the same in animal after animal. Humans and fruit flies share virtually identical genes doing exactly the same things. Some of the best studied are so called "Hox genes." These order development in the fruit fly, and explain why one part comes before another and why one part (say a wing) comes in the wing position and not in the position of another part (say a leg). There are almost exactly the same genes doing almost exactly the same things in humans."

[KT45]

it's amazing how some genes can stay alive for so long. In the book "the selfish gene" it talks about how genes are the ones that control us like preprogrammed robots to keep themselves alive. I just find it incredible how a normally non-existant gene, like one that gives human tails, can still survive for so long!!!

 

I don't consider genes alive, themselves. They're just organic code. And there are much more ancient genes that the tail genes -- by far! The Hox genes have been preserved since right around the beginning!

It's not that they are alive. Dawkins kinda changed the definition of a gene to fit what he was trying to get at. I'm not smart enough to explain. I'm not even smart enough to comprehend what I'm reading as I try to understand the book "The selfish gene". It's just so interesting that I can't put it down. You'd have to read the book and see what you think.

 

Homosexuality – Why would this evolve? Is this genetic?

It's not a genetic trait, but it's psychological. The more older brothers a male has, the more likely he is t be homosexual because his mother's immune system has antibodies against the Y chromosome.

So are you saying that homosexuals are more feminine, since there Y chromosome is affected. There are plenty that are masculine and you couldn't tell which them from a straight guy. Why do you feel it's psychological.

[Amethyst]

Regarding the hair thing:

 

Real-Life Werewolves

 

There are some humans with more than just head hair.

[Callyn]

So are you saying that homosexuals are more feminine, since there Y chromosome is affected. There are plenty that are masculine and you couldn't tell which them from a straight guy. Why do you feel it's psychological.

And there are women with the same interests as any straight guy as well. It's a slight distinction. I didn't say anything abut femininity, just that it's not (in all likelyhood) an inherited genetic trait. That doesn't mean it's any less real or that it's changeable, but from the information we have it's not very likely to have evolved as it wouldn't be passed on all that well.

[KT45]

Homosexuality – Why would this evolve? Is this genetic?

It's not a genetic trait, but it's psychological. The more older brothers a male has, the more likely he is t be homosexual because his mother's immune system has antibodies against the Y chromosome.

http://news.bbc.co.uk/1/hi/health/3735668.stm

Scientists have said it might be that the mother develops some kind of resistance to the male Y chromosome in her offspring that makes subsequent baby boys more likely to be born gay.

 

Scientists doing DNA studies on homosexual brothers pinpointed 'culprit' genetic material to a region of the X chromosome that mothers pass on to their offspring.

 

 

But other researchers in the US have not been able to replicate these findings.

 

but from the information we have it's not very likely to have evolved as it wouldn't be passed on all that well.

http://www.newscientist.com/article.ns?id=dn6519

Italian geneticists may have explained how genes apparently linked to male homosexuality survive, despite gay men seldom having children. Their findings also undermine the theory of a single “gay gene”.

 

The researchers discovered that women tend to have more children when they inherit the same - as yet unidentified - genetic factors linked to homosexuality in men. This fertility boost more than compensates for the lack of offspring fathered by gay men, and keeps the “gay” genetic factors in circulation.

 

The findings represent the best explanation yet for the Darwinian paradox presented by homosexuality: it is a genetic dead-end, yet the trait persists generation after generation.

 

“We have finally solved this paradox,” says Andrea Camperio-Ciani of the University of Padua. “The same factor that influences sexual orientation in males promotes higher fecundity in females.”

 

 

All of this doesn't explain bisexuals but it is interesting

[scitsofreaky]

It's not that they are alive. Dawkins kinda changed the definition of a gene to fit what he was trying to get at. I'm not smart enough to explain. I'm not even smart enough to comprehend what I'm reading as I try to understand the book "The selfish gene". It's just so interesting that I can't put it down. You'd have to read the book and see what you think.

I think you may have forgotten that he uses anthropomophication to help, but it is just a tool. His use of "gene" is vague, meaning a variety of things depending on the situation, but it is always used to mean a grouping of DNA that affect a certain trait.

[Taphophilia]

I know that being able to see well at night is something we give up by having color vision. So, could alertness during the day vs. nocturnal be the reason we developed color vision?

 

Something interesting. Zebra's have black and white stripes for camoflage. The animals that prey upon them are color blind, so zebra's visually blend in with their environment.

[Ziggy]

 

Something interesting. Zebra's have black and white stripes for camoflage. The animals that prey upon them are color blind, so zebra's visually blend in with their environment.

So why wouldn't all 'prey' develop black and white stripes? And how does the gene that makes the black and white in a zerba know the gene in the hunter only makes colour blind eyes!

[Ziggy]

I’ve been reading Richard Dawkins book “The Selfish Gene” and I’m starting to learn more and more about natural selection. Thankfully while in school I was lucky enough to have a teacher that wasn’t religious and tried to teach the subject. Unfortunately I didn’t pay attention as much either because of my Christian background or just because of plain boredom. Before I ask my questions I want to see if I even have a decent grasp of natural selection by giving an example I learned a long time ago in high school.

 

Natural Selection Example: A group of giraffes typically eat from the trees to eat the leaves. One giraffe has a child that has a mutation giving him a slightly longer neck than the others. This giraffe ends up healthier than the other giraffes. It more than likely is able to outrun predators more efficiently than his peers due to his diet. It is also more likely to find a mate to reproduce. After a while that giraffes has offspring that have the same “slightly longer neck” gene as the parent. These giraffes over populate the others. This continues until another giraffe has a mutation that creates a “long neck” gene making him more successful. Over time the giraffes either die out because of lack of food or because finding a mate was too difficult. You now end up having a new species of giraffe that is different from the older species.

 

I recently bought Darwins 'Origin of species' and Dawkins 'The selfish gene' with the hope of of understanding something I was never taught at school or - like you - was so bored I couldn't take it in (I also bought 'Dawkins God' by McGrath thinking it to champion an alternative theory but its more a response to Dawkins Athiesim so we'll leave that aside for now)

 

I have not read all of them yet .. I have a job and three kids and ...well time is of the essence! Plus I do not have a scientific back ground so I have to re read stuff to make sure I comprehend it

 

As you raised this issue I would like to ask my own question on mutation if I may and if I have missed something obvious from the books then the previous sentences are my excuse!

 

My understanding is that mutations are small and fairly rare. Ie the basic genetic code is intact so the new born Giraffe will obviously be a giraffe .. ie very very little difference between one and another. I can accept that the ones with longer necks become more populous but what i want to ask is how other giraffes in other parts of the Africa ALSO 'mutate' in the same way and develope long necks ..when each group may never have crossed paths with the other. Why would one set not figure out a different way of surviving? After all most other animals did not develope long necks so this is not the only way to ensure survival.

 

Say the giraffes were on different islands... would they evolve in the same way or differently and end up completely different species??

 

I understand that there could be visual minor differences like Darwins findings in the Galapagos Island turtles.

 

Also 'mutation' seems a harsh description No two beings are alike ... so ALL have mutations. I would never be exactly like my father in every physical way - similar maybe but not exact This goes for everyone / thing... So that means there is 'mutations' in every generation Surely this is not mutation because that would impy a diffence from a normal. However there is no normal!

 

[Callyn]

So why wouldn't all 'prey' develop black and white stripes? And how does the gene that makes the black and white in a zerba know the gene in the hunter only makes colour blind eyes!

 

Genes don't think and evolution isn't a sentient process. It's just that the animals with certain genes survive more often and take over.

 

My understanding is that mutations are small and fairly rare. Ie the basic genetic code is intact so the new born Giraffe will obviously be a giraffe .. ie very very little difference between one and another. I can accept that the ones with longer necks become more populous but what i want to ask is how other giraffes in other parts of the Africa ALSO 'mutate' in the same way and develope long necks ..when each group may never have crossed paths with the other. Why would one set not figure out a different way of surviving? After all most other animals did not develope long necks so this is not the only way to ensure survival.

 

Say the giraffes were on different islands... would they evolve in the same way or differently and end up completely different species??

 

I understand that there could be visual minor differences like Darwins findings in the Galapagos Island turtles.

 

Also 'mutation' seems a harsh description No two beings are alike ... so ALL have mutations. I would never be exactly like my father in every physical way - similar maybe but not exact This goes for everyone / thing... So that means there is 'mutations' in every generation Surely this is not mutation because that would impy a diffence from a normal. However there is no normal!

 

 

Mutations are very common. Nearly every gamete has some small mutation in it, but most mutatuions are just small and/or don't affect a gene. So every being that comes from sexual reproduction has some new mutations.

 

It's unlikely that all the giraffe populations in Africa evolved the same way. The most likely thing is that one population of an ancestor species evolved and spread over Africa.

 

If giraffes were put on an island, tey would probably evolve in a similar direction (become smaller, as that almost always happens to large animals on islands because there's a lesser supply of resources) but they would evolve into different species wth different adaptations.

 

A mutation (in terms of evolution) is a change in the genetic code of a gamete (sperm or egg in animals). Sexual reprodustion is the reason why no two people are alike, not mutations. Though everyone does have little mutations of their own.

[Entgegen]

I’ve been reading Richard Dawkins book “The Selfish Gene” and I’m starting to learn more and more about natural selection. Thankfully while in school I was lucky enough to have a teacher that wasn’t religious and tried to teach the subject. Unfortunately I didn’t pay attention as much either because of my Christian background or just because of plain boredom. Before I ask my questions I want to see if I even have a decent grasp of natural selection by giving an example I learned a long time ago in high school.

 

Natural Selection Example: A group of giraffes typically eat from the trees to eat the leaves. One giraffe has a child that has a mutation giving him a slightly longer neck than the others. This giraffe ends up healthier than the other giraffes. It more than likely is able to outrun predators more efficiently than his peers due to his diet. It is also more likely to find a mate to reproduce. After a while that giraffes has offspring that have the same “slightly longer neck” gene as the parent. These giraffes over populate the others. This continues until another giraffe has a mutation that creates a “long neck” gene making him more successful. Over time the giraffes either die out because of lack of food or because finding a mate was too difficult. You now end up having a new species of giraffe that is different from the older species.

 

I recently bought Darwins 'Origin of species' and Dawkins 'The selfish gene' with the hope of of understanding something I was never taught at school or - like you - was so bored I couldn't take it in (I also bought 'Dawkins God' by McGrath thinking it to champion an alternative theory but its more a response to Dawkins Athiesim so we'll leave that aside for now)

 

I have not read all of them yet .. I have a job and three kids and ...well time is of the essence! Plus I do not have a scientific back ground so I have to re read stuff to make sure I comprehend it

 

As you raised this issue I would like to ask my own question on mutation if I may and if I have missed something obvious from the books then the previous sentences are my excuse!

 

My understanding is that mutations are small and fairly rare. Ie the basic genetic code is intact so the new born Giraffe will obviously be a giraffe .. ie very very little difference between one and another. I can accept that the ones with longer necks become more populous but what i want to ask is how other giraffes in other parts of the Africa ALSO 'mutate' in the same way and develope long necks ..when each group may never have crossed paths with the other. Why would one set not figure out a different way of surviving? After all most other animals did not develope long necks so this is not the only way to ensure survival.

 

Say the giraffes were on different islands... would they evolve in the same way or differently and end up completely different species??

 

I understand that there could be visual minor differences like Darwins findings in the Galapagos Island turtles.

 

Also 'mutation' seems a harsh description No two beings are alike ... so ALL have mutations. I would never be exactly like my father in every physical way - similar maybe but not exact This goes for everyone / thing... So that means there is 'mutations' in every generation Surely this is not mutation because that would impy a diffence from a normal. However there is no normal!

 

 

Mutations generally are pretty rare. However, with the size of the genome, I've read that each generation has about an average of 3 mutations (good, bad, and/or neutral), so there are usually mutations (albeit not many). But a logical way of thinking about things in speciation is that if two closely-related species (i.e. two varieties of giraffe [are there even multiple species of giraffe?]) share a trait in common, then they share a common ancestor that had that particular trait. So chances are that giraffes developed long necks before they branched off from the common ancestor into the species we know of today.

 

Also, like the whole being like your father thing...although mutations usually occur in every generation, you are unlike your father not by the fact of you having mutations that make you different from your father, but that you have a different combination of genes than your father. You are a product of your father's and your mother's genes (50/50 split), and your father is a product of your grandparents. But even if (this is kinda wierd to think about...) you were your father's brother, you wouldn't be genetically identical (unless you were twins) because of recombination events and things that go on during meiosis, with recombination event being a sort of shuffling of the genes on chromosomes that always happens as sperm and eggs are being made.

 

About the whole zebra thing, not all "prey" species are striped simply because either the mutation for making an originally unstriped animal into a slightly striped animal (evolution through mutation usually doesn't happen in big leaps and bounds like completely unstriped => full zebra-like striped, but a more gradual process) didn't happen, or it did happen and the selective pressures in that particular environment didn't favor it. Genes don't "know" anything...just successful variants of genes get passed on. When (say) an unstriped zebra happened to give birth to a striped offspring, that offspring probably did a little bit better in the environment due to its "pseudostripes" being present, and therefore was able to survive to pass on its genes for making body stripes. Over time, these genes spread out through successive generations due to striped parents generally surviving longer to give more striped offspring, until just about everyone in the population (over a long time) was a striped individual (there are still, on occasion, unstriped zebra offspring being born by the way). Also, another thing I've read, while stripes may help the zebra be somewhat camouflaged, the stripes help break up the outline of individual zebras in a heard, so it would be difficult for a predator to pick out a single zebra when deciding who to go after. Just think about a striped individual in a sea of stripes. By the way, if it's the whole black/white stripes and colorblind predators thing that trips you up, most striped animals aren't black and white. Take tigers, for instance.

[Taphophilia]

Here is something that I have been thinking about. Humans because of our brains don't have natural selection anymore the way we once did. We have access to technology to help us overcome some of the problems where death would occur and genes are being passed on where they normally would not be.

 

For instance, in developed countries we have C-sections for births of babies that would never have been born naturally and helping women whose birth canals are too small for natural births to pass on their genes. Premature babies now have a great chance of survival. However, developing countries do not have this.

 

Would humans eventually evolve into different types of humans? Those who have evolved with technology and those who have not? Wouldn't the humans who do not have technology evole faster than those who do, since they have more children and at younger ages.

[Entgegen]

Here is something that I have been thinking about. Humans because of our brains don't have natural selection anymore the way we once did. We have access to technology to help us overcome some of the problems where death would occur and genes are being passed on where they normally would not be.

 

For instance, in developed countries we have C-sections for births of babies that would never have been born naturally and helping women whose birth canals are too small for natural births to pass on their genes. Premature babies now have a great chance of survival. However, developing countries do not have this.

 

Would humans eventually evolve into different types of humans? Those who have evolved with technology and those who have not? Wouldn't the humans who do not have technology evole faster than those who do, since they have more children and at younger ages.

 

There's a book out by a guy named Joel Garreau called Radical Evolution that talks about the next possible stages in human evolution, all having to do with humans being integrated with the new technologies being explored today. He calls them the GRIN technologies: Genetics, Robotics, Information technology, and Nanotechnology. He tells of some of the things being tested and experimented on today (some pretty far-out stuff that they've made more headway on than you'd imagine), then presents three possible scenerios: Heaven, Hell, and Prevail. Heaven is basically technology becomes so ingrained in humans that we usher in a wonderful new stage of human nature. Hell is the exact opposite: technology gets away from us and we're fucked. Prevail is a combination between the two; we realize the potential for things and we really guide things so that they don't get out of hand. These scenarios are all highly speculative, but all in all, it's a pretty neat book, and I recommend it.

[Taphophilia]

That sounds like a very interesting book, thanks. I think advanced technology, like advanced medicine, is something that not all humans will have access to. Will this be the next "natural selection" for humans?

 

I do believe the future of humans will involve the incorporation of technology. Yes, we can speculate and make educated guesses, but I would think that whatever happens to us will be completely different than anyone can ever imagine.

[Reverend AtheiStar]

It's not that they are alive. Dawkins kinda changed the definition of a gene to fit what he was trying to get at. I'm not smart enough to explain. I'm not even smart enough to comprehend what I'm reading as I try to understand the book "The selfish gene". It's just so interesting that I can't put it down. You'd have to read the book and see what you think.

 

I have the book, actually, and I've read the beginning. But I never finished it because at the time it was a book I had rented from the library. My wife ordered it not too long ago from mail order but I haven't gotten around to reading the rest of it. Perhaps I should dust it off and crack it open once more.

 

If you haven't, I'd pick up Ancestor's Tale. I found it much more informative in the way of evolution because he uses a backwards chrnology and it really helps one to envision the process! He even goes back to all the hypotheses regarding chemical evolution or abiogenesis! He takes his time to describe all the latest scientific evidence for each position, too. It's a wonderful read.

 

 

 

That sounds like a very interesting book, thanks. I think advanced technology, like advanced medicine, is something that not all humans will have access to. Will this be the next "natural selection" for humans?

 

I do believe the future of humans will involve the incorporation of technology. Yes, we can speculate and make educated guesses, but I would think that whatever happens to us will be completely different than anyone can ever imagine.

 

The latest natural selection with humans, as I see it, is with metabolism and our fat laden diet. Those who don't have high metabolisms are dying off. This culling is what shapes species. It was the opposite for eons. In places where food was scarce, the high metabolisms died off and the more heavy, slower types proliferated. Another would be with head, and hence brain, size. There was a restriction on the size of head that could fit through theb hips and out of a vagina. Now, with the massive success and popularity of the c-section, larger brained humans could easily come to be. We also tend to be going toward less and less hair on our bodies. These are all very easy things for evolution accomplish.