quote:
When is the last time someone asked a question like this: can the small changes that we observe today be extrapolated to big changes with enough time?
It's a valid question. The evidence is that they can.
We know now that all differences between organisms (with some marginal exceptions) are accounted for by differences in DNA sequence. Between two kinds of organism - say chimps and humans - there is always a series of changes to DNA that will transform one into the other, a vast number of such in fact.
There is clearly no constraint on how many changes can take place over time, so that's not a problem, and we know that these changes take place at the right rate according to estimated dates of divergence.
The only question is - is there pathway in which each of those intermediate steps is viable, ie will successfully reproduce? Or more accurately, for a given degree of difference is there always some step in the path between the two organisms such that a single step (point mutation, duplication, indel etc) is not going to be viable?
There is no evidence that this is the case, and no proposed mechanism that would enforce this kind of limitation.
Evidence from genetics, on the other hand, particulary the strong evidence of common descent, shows that change on this scale HAS occurred.
Therefore we are justified in saying that small changes can add up to large.
Edited by Peepul, : Clarity
™ Version 4.2
