Evolution

[Evan]

I was reading around on a few sites about evolution and this question came up "How come enough members of a species develop a new trait that will survive on to the next generation? Why does a random mutation appear in more than one creature?

 

I thought it was a really good question, but I only know basics of evolution so it has probably already been answered numerous times.

 

My guess is that it takes time for a good gene to spread enough into other gene pools. One creature develops a good trait and then breeds. The part of the litter with the gene surive and go on to reproduce. So the better trait would pass on, but like macroevolution... it would take time?

 

How cold am I?

[Thurisaz]

I'm not exactly an evolutionary biologist, but as far as I know, you're quite close to home there.

 

Let alone that there's always some mutation and variation in a population. I wouldn't rule out that there's always a certain percentage of individuals born with a trait that under "normal" circumstance doesn't matter, but guess what happens if the environment changes and that traid suddenly becomes an advantage.

 

After all, to just spread throughout a population a trait doesn't have to be an advantage... it just mustn't be a disadvantage.

[Ouroboros]

I think the "survival of the fittest" is a bit misleading, because it's more like "death of the unfit" when you think about it. A mutation can be neutral and hence stick around for a while, and then mutate again and become and advantage or disadvantage later on.

 

There are even mutations that are considered genetic defects that are killing people, but came about because these genetic traits actually helped people survive the plague and other disasters. I can't remember which one right now, but I heard a while back there is a blood sickness that can be explained by that a large population survived the black plauge (I think) because of this blood sickness. Weird. There's a book about it. I'll see if I can figure out what it was called and get more details tomorrow.

[Thurisaz]

The classic example (maybe that's what you're thinking of Hans) is sickle cell anemia. Basically it'sa heritable disease producing malformed erythrocytes. it would suck royally if not...

 

...if not...

 

...it would just happen to make people (mostly?) immune to malaria.

[Ouroboros]

Yeah, that's one of them. Thanks. I just can't figure out what the book was called.

 

Oh, the other genetic disesase: hemochromatosis. From what I remember it gave a protective benefit against the bubonic plague.

 

Ah, the book: Survival of the Fittest, by Dr. Sharon Moalem.

[scitsofreaky]

How come enough members of a species develop a new trait that will survive on to the next generation? Why does a random mutation appear in more than one creature?

It is a good question. One possible way I have read about it targeted mutation. What this means is that in some species in some circumstances some genes, let's say ones involved in producing venom, have their mutablitly increased by cellular mechanism (probably, the ones involved in gene regulation and maintenance). This would increase the likelihood that multiple individuals in a population have the same mutation because a smaller part of the genome is affected.

Also you have to keep in mind that different genotypes can lead to the same phenotype. So you can have different individuals with the same trait even without having the same mutation(s).

 

I can't remember which one right now, but I heard a while back there is a blood sickness that can be explained by that a large population survived the black plauge (I think) because of this blood sickness.

Crap, that is really bugging me. I know I know which "disease" it is, I just can't think of it. I might have heard that people with the same "disorder" are possibly resistant to HIV. But don't quote me on that.

 

After all, to just spread throughout a population a trait doesn't have to be an advantage... it just mustn't be a disadvantage.

Well, yes and no. A trait is more likely to spread if it is advantageous than a neutral one, just as a neutral one is more likely than a harmful one. But I took that quote a bit out of context, and in context it is a good point.

[Ouroboros]

I can't remember which one right now, but I heard a while back there is a blood sickness that can be explained by that a large population survived the black plauge (I think) because of this blood sickness.

Crap, that is really bugging me. I know I know which "disease" it is, I just can't think of it. I might have heard that people with the same "disorder" are possibly resistant to HIV. But don't quote me on that.

Right. I got it, it's hemochromatosis. It makes a person to rust from inside and die a painful death where liver functions fail and much more. But just with a little blood letting they'll be fine. They just donate blood on a regular basis and they'll live a normal life.

 

And I don't remember if they're the ones with the HIV restistence or not, but I've heard that some European heritage does have that trait.

[Evan]

Thank guys... appreciate the answers

 

as for this plague stuff... its good to know that people survived because they would get the lesser of two evils

[scitsofreaky]

And I don't remember if they're the ones with the HIV restistence or not, but I've heard that some European heritage does have that trait.

I think what I saw was just about how they (whoever "they" are) were still looking at the link between the plague and HIV, so I'm sure that's why hemochromatosis came up. I haven't heard anything since, so who knows what, if anything, they discovered.