Couple Of Evolution Questions

[Wertbag]

I was having a discussion about evolution and had a couple of points raised that I'm not sure on, so I thought I pass it out to help fill the gaps in my knowledge.

Does evolution slow in larger populations? Theoritically if someone was born today with a great genetic change (immune to Aids for example), their total impact on the human population must be quite small. Even with a large family tree the total penetration of this good gene would be quite limited. Is it therefore possible to say evolution would have ceased for mankind as our population would restrict these changes?

If someone has a beneficial gene but it is not one that will directly effect their chances of spreading their genetic code (eg immune to Aids yet ugly as hell), theoritically we would lose genetic code as people fail to have children or are killed too early in their life. This would therefore mean that superficial changes to make people more attractive would be more likely to be passed on than useful ones such as immunity to diseases. Will this mean that mankind will get prettier but not necassarily improve genetically over how we are now?

And finally if humans are using technology and medicine to overcome genetic defects which in the wild would have either killed or at least caused that person to have no offspring, are we therefore changing our evolutionary course as well? Could our technologies use to keep bad genes in our gene pool have a negative impact on mankind?

 

Any information appriciated.

[scitsofreaky]

Wow, those are some great questions.

The first two I don't have a specific answer for. But I will say that evolution via natural selection means that genotypes that give individuals reproductive advantages will on average become more common. You really can't talk in absolutes when dealing with genes spreading in a population.

I am in the group that thinks that because of globalization natural selection is at least restricted because the gene pool is so large. I wouldn't go so far as to say that it has ceased because there are still, and probably always will be, relatively small pockets of people that will remain somewhat reproductively isolated. But it is hard to say because evolution is on such a large time scale. It is hard, if not nearly impossible, to even look back at human history and find changes that can be credited to genetic variation instead of some other variable, such as nutrition.

And finally if humans are using technology and medicine to overcome genetic defects which in the wild would have either killed or at least caused that person to have no offspring, are we therefore changing our evolutionary course as well? Could our technologies use to keep bad genes in our gene pool have a negative impact on mankind?

First and foremost, there is no "evolutionary course." Because of this, one cannot argue that we are somehow screwing up our future.

A gene can only be considered "bad" if it causes the individuals with it to not be able to reproduce in the environment it lives. If the environment includes medicines and therapy, then so be it. But as long as the gene doesn't give an advantage, there isn't much reason for it to spread, it just wouldn't die out.

This seems to relate to eugenics. I am against eugenics for a few reasons. One, it takes away rights. Right there is enough reason for me. Second, IMO we are too myopic and superficial for any real good to come about. But that's purely opinion.

 

I hope that I was at least some help.

[Entgegen]

I was having a discussion about evolution and had a couple of points raised that I'm not sure on, so I thought I pass it out to help fill the gaps in my knowledge.

Does evolution slow in larger populations? Theoritically if someone was born today with a great genetic change (immune to Aids for example), their total impact on the human population must be quite small. Even with a large family tree the total penetration of this good gene would be quite limited. Is it therefore possible to say evolution would have ceased for mankind as our population would restrict these changes?

If someone has a beneficial gene but it is not one that will directly effect their chances of spreading their genetic code (eg immune to Aids yet ugly as hell), theoritically we would lose genetic code as people fail to have children or are killed too early in their life. This would therefore mean that superficial changes to make people more attractive would be more likely to be passed on than useful ones such as immunity to diseases. Will this mean that mankind will get prettier but not necassarily improve genetically over how we are now?

And finally if humans are using technology and medicine to overcome genetic defects which in the wild would have either killed or at least caused that person to have no offspring, are we therefore changing our evolutionary course as well? Could our technologies use to keep bad genes in our gene pool have a negative impact on mankind?

 

Any information appriciated.

 

I might be able to help out a little bit with your questions. As for the first, in general, evolution through gradual natural selection occurs more rapidly in small populations, since one individual with a beneficial phenotype has a relatively minor impact on a large population. However, large populations are still subject to selection, such as a (generally rare) catastrophic natural disaster. Say a horrible pandemic swept the globe, eliminating all but a few groups of people who just happened to be resistant/immune to the disease. Those few people, provided they have the resources, will then have the opportunity to repopulate with offspring containing the beneficial phenotypes. So, while we humans don't really seem to be evolving much now, we are still subject to selection pressures.

 

As for the second, in general, alleles (different forms of genes) are beneficial if they increase fitness, which is the ability to produce offspring. So, alleles that negatively impact our ability to have kids (whether the result is that we die before we are sexually mature, or renders us incapable of finding a mate, or whatever) are usually weeded out. So yes, if something aids us in passing on our genes while slightly hindering our ability to survive (such as something that makes us more attractive to the opposite sex at the expense of disease immunity), in general it will be conserved within the population so long as the downside isn't too devastating to the individual's ability to survive to sexual maturity. Now as far as humans becoming more "pretty" over time, everyone has a different definition of what is "pretty" and what isn't, so you will always have a hodge-podge of varying physical traits within a population.

 

For your last question, this doesn't have any sort of clear cut answer. I personally feel that technology has definitely impacted what human traits survive within a population, since we have the power to manipulate the selective pressures that would otherwise surely eliminate non-desireable traits. Now, what sort of impact will this have on us as a species is open to debate, and there's a pretty cool book over this very topic called Radical Evolution by Joel Garreau. The author outlines several scenarios of humanity's fate in light of modern technology by speaking with proponents of each scenario. It's all pretty subjective, but it's really interesting.

[Saviourmachine]

Does evolution slow in larger populations? Theoritically if someone was born today with a great genetic change (immune to Aids for example), their total impact on the human population must be quite small. Even with a large family tree the total penetration of this good gene would be quite limited. Is it therefore possible to say evolution would have ceased for mankind as our population would restrict these changes?

There are several factors involved in "the speed of an evolutionary adaptive process".

1. The selective pressure of aids. In Africa the selective pressure of malaria is such that even sickle cell anemia is considered beneficial by mother natural selection.
   
2. The size of the population. More generations needed to cover the population.
   
3. The dynamics in population size. Bottlenecks and explosions.
   
4. Environmental changes. The environment evolves too. We wouldn't be here if it was still 1000 degrees Celcius.
   
5. Direct intervention. Only recently humans are capable to select upon genotype rather than fenotype.
   

If someone has a beneficial gene but it is not one that will directly effect their chances of spreading their genetic code...

Beneficial should be defined as chance of spreading genetic code. People that are attracted to not-attractive people that are immune to diseases will have more children.

So, more probable is that appearance is in some way a reflection of someones good genes. The peacock spills its energy to its feathers to show that it can afford that and still survive, yeah even reproduce (sexual selection).

And finally if humans are using technology and medicine to overcome genetic defects which in the wild would have either killed or at least caused that person to have no offspring, are we therefore changing our evolutionary course as well? Could our technologies use to keep bad genes in our gene pool have a negative impact on mankind?

Several points.

• In this case you see humans as "outside the system". Humans are IMHO part of the environment. The super-humans in the future will be the result of selective pressures of their entire environment (including humans).
  
• Cultural selection will play a big role. If someone is a kind of vagabond and does not fit into this or that society, than his chances upon reproduction decrease. In former times such person could have raped a woman, and reproduce nevertheless. Nowadays she would abort the child. Small example, the traits selected for, change!
  
• To keep bad genes in our gene pool is impossible. Take the world from a gene-viewpoint. A gene is beneficial if it reproduces. In this case its reproduction becomes dependent on selective pressures of nature, the other gender, and certain technologies. The "bad" thing involved is dependency on techniques. Humans may fill a niche formed by mother nature and father technology and become extinct when one of those environments change abruptly.
  
• There is no "mankind", we are a branch on a tree, perhaps a step on a ladder.
  
• If we do not use our technologies in the right way we don't have the right to survive. Another specie will take our flag.