Human Evolution: A Facebook Dialog
Sometimes it might be a good idea to actually read what ID proponents write before critiquing it.
Recently a video clip of me discussing the time required for human evolution was released. Everything in my interview was based on material in our book Science and Human Origins, published last June. I posted a link to the video on Facebook.
The video attracted the attention of some critics, one of whom decided to question what I meant by time limits, among other things. Below is the final part of the exchange. I have taken the liberty of juxtaposing the answers to the appropriate questions, since the time delay on Facebook sometimes means that answers and questions get intermingled.
PM: In terms of time limits, are you referring to 6,000 years or 4.5 billion years?And that ended that conversation, abruptly.
Biologic: The time limit is the time of the supposed divergence of the chimp and human lineages. Estimates for that divergence vary from 4-6 million years, to more recent estimates of 7 or 8 million years.
PM: So the time could be double what some estimates suggest? Is it possible that the time could be even earlier?
Biologic: The time of divergence is an estimate based on other estimates, including the average mutation rate in the primate lineage. I have seen no estimates older than 8 million years.
PM:Is it also possible that the mechanism that you refer to in your video clip is not the only/main one at play?
Biologic: The mechanism I refer to is based on the standard Darwinian model for evolution. Published population genetics estimates for how long it would take to make *and fix* a single base change to a DNA binding site in a 1 kb segment of DNA are prohibitively long--six million years. To get a second mutation in the same DNA binding site would take in excess of 200 million years.
Now to go from hominid to human requires many changes, most of them to gene expression patterns. It is much easier to change the DNA binding site than to change the transcription factor's specificity. And all these mutations must work together and be beneficial to the evolving organism. The window of time available according to the fossil record and phylogenetic estimates is too short for known mechanisms to be sufficient. So do I think there are are other things at play? Yes.
PM: This sounds remarkable. Why did you not publish this in either Nature or Science?
Biologic: It's already published, not my work.
You can see the whole exchange here.
Why not become a Facebook friend while you are there?
Cross-posted at Biologic Perspectives.