Did 90% of Animal Species Appear about the Same Time as Human Beings?


(system) #1

This is a companion discussion topic for the original entry at https://biologos.org/blogs/archive/did-90-of-animal-species-appear-about-the-same-time-as-human-beings

(Phil) #2

Good explanation. Also discussed on this thread:


(Steve Schaffner) #3

I’m not fond of the leap from “most recent mitochondrial ancestor” to “bottleneck”. There was a most recent mtDNA ancestor with or without a bottleneck. That the times of the most recent common ancestors seems similar for a lot of species might be telling us that many of them went through a bottleneck around the same time, or it could be telling us that they have similar effective population sizes, or it could be telling us that the effective population size of mitochondria is limited by natural selection. Since humans fall into this group, and human nuclear genomes show no sign of a major bottleneck in the relevant time period, bottleneck should not be the default explanation. @Joel_Duff


#4

The other potential problem that jumps out at me is relying on a single 600 bp stretch of mitochondrial DNA to give us an accurate picture of population dynamics over the last million years. I tend to agree with the authors that DNA barcoding does appear to be a useful tool for identifying species, but I also have my doubts that it can be useful in mapping past population dynamics.


(Dennis Venema) #5

It’s for this reason that I can’t figure out why people (including the authors) suggest a bottleneck to explain their observations. A more interesting calculation (IMO) would be trying to understand how likely it is for a population (of a given effective size) to maintain mitochondrial diversity over a longer timeframe.

That and equating “last common mitochondrial ancestor” with “beginning of a species” - uh, excuse me? :slight_smile:


(Joel Duff) #6

I’m in the Canadian hinterlands for the next few days so I’m not checking my mail much. I agree with your assessment here. I meant the bottleneck to be one example of several possible explanation for their data. In chopping down the article it was left that simple example of how some mDNA lineages could be eliminated leaving the last common ancestor much more recent than the species origin. Certainly, no all species, or even most, underwent population bottlenecks but there are many other ways in which mtDNA lineages are sorted over time resulting in many lineages going extinct. So, yes, my article is skewed to that single example to make the main point clear about species vs mtDNA ages. @T_aquaticus @DennisVenema