Re: Transitional / intermediate
Posted: Tue Dec 13, 2016 8:10 am
That was what I meant really. Eventually (after many generations) a population would have developed a change. I talked about natural selection a bit in the evolution thread.Audie wrote:In a whole population..like if everyone on earth started having babies who were part of a genetic change to, say, feathers?Nicki wrote:That could be right, but I'm talking about even smaller changes. How many generations would it take for feathers to develop in a whole population? Quite a large number, I'd say - but as Audie has said before, most organisms die without being fossilized and there might be many fossils that haven't been found yet.hughfarey wrote:This is a valid point, the first one on this topic which makes some sense. If every animal is fully formed and adapted to its environment, how come we have dozens of fossils of land-dwelling, unfeathered, unflying "ancestors" of birds, and dozens of tree-dwelling, feathered, flying birds, but remarkably few fossils of animals adapted to environments intermediate between the land and the trees.Nicki wrote:I think the idea is that there should be many more transitional forms (with very little change between them) in between the fairly different creatures that we have fossils for - we just have a 'fully formed' this or that animal with noticeable gaps from one to the next.
Actually putting it like that helps to explain the reason. There is a lot of land, and there are a lot of trees, but the ecological niches that require a reptile with feathers, or a bird with four claws, are few. There are some - even today we see the remarkable hoatzin - and before competition from other birds and mammals outperformed them there were more, but the evolutionary bottleneck, both environmentally and in time, meant that there really were fewer intermediate species between reptiles and birds, which consequently left fewer fossils.
Something similar can be seen with the organisms intermediate between fish and reptiles. There is a lot of water, and a lot of land, but rather less environment between the two, which is perhaps why there are many fewer riparian amphibians, even today, than fish or reptiles.
It doesnt work that way.
Think of the fly that was resistant to DDT. After a bit, all flies would be descendants of the resistant strain. The whole population didnt develop it, they inherited it.