Originally posted by jiggerj
How do these sub-species come about? I imagine that a tribe of one species splits up. Half of them stay where they are and never change. The other
half goes off to face adversities in a new environment which causes them to evolve in certain ways in order to survive. Then that tribe splits up, and
so on and so on...creating thousands of branches and sub-species.
Under this premise how could EVERY SINGLE branch die out and leave only us here today? Doesn't that seem highly improbable? Not only improbable, but
for evolution to have worked this way it would have taken (in my opinion) billions of years.
You are correct in the first paragraph, but also interbreeding takes place among many sub species, so the genes split up and change, but then come
back together thousands to millions of years later increasing genetic diversity.
The extinction of other intelligent hominids on earth is a mystery right now. Homo sapiens being the only intelligent beings, is relatively new,
however. Just 20,000 years ago we shared the planet with several different other hominids and subspecies. Perhaps a natural disaster wiped most of
them out. It may have had to do with the end of the last ice age or an impact event. Maybe homo sapiens killed the others off. We know sapiens and
neanderthalensis bred together, as well as Denisovans and another mystery species. If you look in nature, there are many more sub species, but a line
dies out when a disaster happens and they cannot adapt. For whatever we, we did while the rest perished. It could have been our location or numerous
Evolution and the rate of change is dictated by the environment. If a creature is well adapted there is no need for change. Sharks are a great
example. They predate dinosaurs by like 200 million years. Yet, white sharks are still here and almost exactly the same, just a bit smaller.
Also that skull picture is obviously photo shopped. I don't know if that was intentional to show what happened, or what, but it's obviously not 3
skull samples separated by millions of years. I didn't even think they had more than 1 skull sample of afarensis.
edit on 31-8-2012 by Barcs
because: (no reason given)