Survival of the fittest

lindagarrette · 03-13-2005

It is my understanding that a mutation which causes sufficient advantage for the beings who have it to survive while the others can't is evolution. Yet, I recall from the old Cosmos series when Carl Sagan showed some Japanese fisherment throwing back crabs that had face formations which lead to their eventual selection over those that didn't. What if some environmental or even unnatural condition occurred so that only blond people were able to live and reproduce. Would that make them a different species? That doesn't seem like evolution, to me, unless you consider the hair color trait to be a mutation. Am I way off base here?

Will · 03-13-2005

i don't know what inspired you to think of this scenario, but as you said unless being blonde was a mutation it wouldn't be evolution. blonde hair is just one physical trait of many which humans have.

Tormod · 03-13-2005

"Survival of the fittest" is a misconception according to George Williams, author of "Plan and Purpose in Nature". Herbert Spencer coined this phrase based on Darwin's theories, but Darwin was talking about adaptation as one weapon for survival. Being "fittest" is not always the case.

The crabs were thrown back into the sea because they looked like a face from a Japanese fairy tale. So they are favored now. But only NOW, and only by humans. And who knows for how long? And humans are most likely not their only enemies. So their looks probably do not help them much at all.

bumab · 03-14-2005

Quote:

Originally Posted by lindagarrette

Would that make them a different species? That doesn't seem like evolution, to me, unless you consider the hair color trait to be a mutation. Am I way off base here?

The whole species concept is a little murky in biology. It used to be interbreeding- if you could, you were the same species. If not, you were different. But, that's not really the case anymore, because there's so many exceptions. According to that idea (which is still popular), blonde folk would not be a different species because they presumably could still interbreed with the rest.

A good species concept (i think) is niches. If two species occupy the exact same niche, one will go extinct. So, everything that occupies the same niche is either the same species or one species on it's way to dominence or extinction. If the blonde folk were not breeding with the rest of the survivors (other haired folk), and still using the exact same resources, they would eventually either go extinct or drive the rest to extinction. So they would be seperate species...

I'm not explaining that idea very well, am I? Hmmmm.... the whole species concept is pretty interesting, though.

TeleMad · 03-16-2005

Quote:

Originally Posted by bumab

A good species concept (i think) is niches. If two species occupy the exact same niche, one will go extinct.

Competitive exclusion...

Quote:

bumab: So, everything that occupies the same niche is either the same species or one species on it's way to dominence or extinction.

Then how is that a good concept of a species? You just acknowledged that you couldn't tell if what you are looking at is one or two species.

TeleMad · 03-16-2005

Quote:

Originally Posted by Tormod

"Survival of the fittest" is a misconception ... Herbert Spencer coined this phrase based on Darwin's theories ...

And then Darwin adopted it himself, even saying that he felt it was in some ways preferable to his own term natural selection.

zadojla · 03-16-2005

You also have to remember what "natural selection" really means: having more surviving offspring in subsequent generations. It says nothing about the physical survival of the individuals under study.
And then there's the whole murky subject of altruism.

TeleMad · 03-16-2005

Quote:

Originally Posted by zadojla

You also have to remember what "natural selection" really means: having more surviving offspring in subsequent generations. It says nothing about the physical survival of the individuals under study.

Sounds a bit self-contradictory. But more importantly, natural selection DOES also deal with the physical survival of the individuals ... if you don't survive, you can't reproduce. For example, cryptic coloration in the peppered moths. Both dark and light moths existed, but nature began favoring the dark ones because of differential predation. Because fewer dark moths were eaten, dark moths got to reproduce more often than light moths. Darkness didn' make them extraordinary lovers or give them extraordinary sexual organs....it just made them more likely to survive. It was differential survival that caused differential reproduction.

zadojla · 03-16-2005

Think about cases like male black widow spiders. If they survive, they don't reproduce. (How such a situation would evolve I am not qualified to explain.) Selection is not only survival, but reproductive selection as well.