Expert: John Shea - 5/15/2007

Question
Hi John! I have an assignment & I'm stuck on one question because I don't really understand what it's talking about. The question reads, "While the mechanism of microevolution is generally accepted, the process of macroevolition, especially as it pertains to hominid evolution, is not. Define and explain two reasons to account for this difference in acceptance and what kind of evidence would be needed to support the validity of macroevolution." I've read up on macroevolution and can't think of what kind of evidence would be needed to make this theory accepted. Could you try helping me? Thanks so much!

Answer
Hi Shannon
I'm not going to answer a homework question for you.  That would be unethical, but, I can push you in the right direction.
Microevolution (changes in gene frequencies) can be measured relatively easily, at least among experimental populations that reproduce quickly and in large numbers (e.g., fruit flies).
Macroevolutionary processes involve longer-term processes operating across multiple generations.  Such changes are less easily observed in experimental populations.
With hominin evolution, you are limited further still, in that (1) it is unethical to conduct controlled evolutionary experiments on hominins, (2) we reproduce very slowly.
A further difficulty in linking micro- to macro evolution is that we still do not know the particular genetic basis for many of the morphological structures that directly influence individual (vs. gene) fitness.
One last thing, any textbook that asserts that there is any doubt among scientists that macroevolutionary processes (sexual selection, extinction, for example) were involved in human evolution is grossly misrepresenting the scientific consensus.  Seen any australopithecines lately?
Cheers,
John Shea