Ann Gauger's latest salvo against Dennis Venema's arguments against an original pair of human beings


#1

Just to keep everybody updated: Does science rule out a first human pair? Geneticist Richard Buggs says no.


God: a failed hypothesis or something more?
#2

What I find interesting is the fact that neither Gauger nor Buggs discuss how many generations it would take to produce the observed genetic diversity in the human population after a bottleneck. Is it 100,000 years? Is it 1 million years? All we get is vague assertions like this one:

“Buggs goes on to discuss the relative genetic diversity of chimpanzees at 5.7 million SNPs (single nucleotide polymorphisms) and humans at 3.1 million (Prado-Martinez et al 2013 Nature). He makes the point that if a pair of chimpanzees were moved to an isolated region where rapid population growth was possible, the new population would have similar levels of genetic variability to modern humans.”

They also tend to focus on heterozygosity vs. homozygosity which really misses the boat. The evidence for a lack of a bottleneck is the number of alleles at each locus. For example, for some of the HLA genes there are thousands of alleles.

Gene: # of alleles
HLA-A: 3,968
HLA-B: 4,828
HLA-C: 3,579
http://hla.alleles.org/nomenclature/stats.html

If we start with just 2 people that is a max of 4 alleles for each of these genes. I just don’t see how you can go from 4 alleles to 4,000 alleles in just 6,000 years, and have those alleles spread so evenly across the globe.

They also use a bit of misdirection:

“Effective population size is very hard to determine. In fact, in some situations the effective population size cannot be determined (On the Meaning and Existence of an Effective Population Size P. Sjödin, I. Kaj, S. Krone, M. Lascoux and M. Nordborg (2005) Genetics 169: 1061–1070). So any estimates concerning effective population size should be taken a bit skeptically.”

To use an analogy, that is like saying it is difficult to accurately measure the orbit of an asteroid, therefore you can not claim that asteroids orbit the Sun. Even with limited accuracy we can still rule out many scenarios, and that is the case with a drastic bottleneck in the recent history of the human population.

What they need to do is use the standard equations from population genetics and show that the observed levels of human genetic diversity could be produced in such a short time. Without such a demonstration they are just blowing smoke.


(Jay Johnson) #3

Apparently, they are building a smoke generator. From the linked article:

“What is needed is a model that does not rely on the standard assumptions of population genetics. Recently Hössjer, Gauger, and Reeves have proposed such an alternative model. The model, when programmed, will be available for use by anyone to test the effects of various starting conditions …”


#4

I’m pretty sure neither Gauger nor Buggs is a Young Earth Creationist.


#5

Then they need to provide the time frame they are talking about, and the math to back it up.

Until then, the findings found in several peer reviewed papers stands. One of the stronger pieces of evidence is the SNP/LD (single nucleotide polymorphisms/linkage disequilibrium) data that Venema discusses in this paper, starting on page 174. These calculations only use variation in the human population and don’t depend on the assumption of shared ancestry with other apes. What it does is study mutations that are close to one another that wouldn’t be as strongly influenced by recombination. It takes time and a larger population to build up mutations next to each other in the genome.


(Curtis Henderson) #6

I don’t know enough about Gauger to guess, but I found this quote from Buggs interesting:

Other scientists have argued against Venema’s position by disputing key assumptions, including the idea of common descent. Buggs’s argument is valid, though, whether or not common descent is true. In fact, he has told me he is assuming common ancestry, but arguing that we can still have come from a single couple as ancestors.

It sure sounds as though Buggs accepts common ancestry, but why would he be disputing evidence suggesting a larger beginning population of humans unless he thinks Adam and Eve were truly the only two original Homo sapiens?


#7

Buggs writes:

“In general, I am concerned that the studies you cite did not set out to test the hypothesis that humans have passed through a single-couple bottleneck. They are simply trying to reconstruct the most probable past effective population sizes of humans given the standard assumptions of population genetic models. I personally would feel ill at ease claiming that they prove that a short sudden bottleneck is impossible.”

Is Buggs mistaken?


(Curtis Henderson) #8

I have not yet read my copy of “Adam and the Genome”, so I don’t know how strongly Venema actually makes his claim. Personally, I would hesitate to say that a 10,000+ initial human population is as certain as heliocentricism, but I think the evidence does support the larger initial population size. Buggs might have a point regarding the strength of the claim, but Gauger certainly pounces on the possible overstatement with overzealous vigor!


#9

I suggest you re-read Gauger:

“Finally, given Buggs’s critique, Venema’s claims that our starting population was at least 10,000, and that we could not have come from just two, seem unjustified. Certainly Venema cannot claim these are facts as sure as heliocentrism. He should at least acknowledge the facts above, and soften his claims. Further revision may be necessary following the results from Hössjer, Gauger, and Reeves’s model. We shall see.”


(Curtis Henderson) #10

I don’t know what you think I should re-visit.


#11

Your claim that Gauger “pounces on the possible overstatement with over zealous vigor!”

Venema was the one who made the comparison to heliocentricism, not Gauger.


#12

If the estimates are 5,000 to 10,000 for the effective population size (which is going to be smaller than the actual population size), then the probability of there being just two humans in the past is so improbable as to be ignored. It’s like a farmer estimating the weight of a bull at 2,000 lbs, and having someone say that estimates can be inaccurate, so the bull could weigh 2 lbs. The chances that a farmer would mistake a 2,000 lb bull for a 2 lb bull is bull . . . well, you get the picture.


#13

All we are seeing is assertions that lack any evidence to back them, and an allusion to some population model that hasn’t been published or peer reviewed. On the other side, we have Venema who has cited several peer reviewed papers and uses the standard equations for population genetics that have been used in peer reviewed papers for decades. It is pretty easy to see that the science is on Venema’s side.


(Curtis Henderson) #14

Yes, I’m aware of that and never said anything contradictory to that point. My point was that if Venema did overstate, Gauger pounced on it and is trying to stir up some controversy.


#15

T, I will just restate the quote from Buggs:

“In general, I am concerned that the studies you cite did not set out to test the hypothesis that humans have passed through a single-couple bottleneck. They are simply trying to reconstruct the most probable past effective population sizes of humans given the standard assumptions of population genetic models. I personally would feel ill at ease claiming that they prove that a short sudden bottleneck is impossible.”

Is Buggs mistaken?


(George Brooks) #16

@DennisVenema,

Is there a simplified equation that we could see, if not actually manipulate ?

Something like this:

Population Premises for Trait “A” (Rapid Allele Production):

  1. Premise 1: Approx. Number ___ of Unique Alleles for Trait: “A”________ in Human Genome.
  2. Premise 2: Average # of Years ______ to Produce Number ____ of New Alleles for that trait.

Population Premises for Trait “B” (Slow Allele Production):

  1. Premise 1: Approx. Number ___ of Unique Alleles for Trait: “B”________ in Human Genome.
  2. Premise 2: Average # of Years ______ to Produce Number ____ of New Alleles for that trait.

Population Premises for Trait “C” (Average between Fast & Slow Allele Production)

  1. Premise 1: Approx. Number ___ of Unique Alleles for Trait: “C”________ in Human Genome.
  2. Premise 2: Average # of Years ______ to Produce Number ____ of New Alleles for that trait.

I know this is a grotesque over-simplification… but what else would we need to come up with a very rudimentary number?

George


(Dennis Venema) #17

I’ll have a reply to Gauger in a few days. So many things to write, so little time… :slight_smile:


(George Brooks) #18

@DennisVenema,

Please, put your response to Gauger on the front burner … we are all interested in seeing it!

Thoughts on my question can come at a more convenient time … if not in the process of your responding to Gauger !

:smiley:


#19

Buggs’ opinion is immaterial unless he has evidence to back it up.


#20

It would also be nice if @glipsnort could chime in. His popgen-fu is much stronger than mine. I know that he has done calculations in the past for population sizes needed for producing n alleles that appear in at least 1% of the population, and other pertinent calculations.