Why "Y-haplogroup Adam" and "mtDNA Eve" Calculations Don't Matter for Origins Questions

The "Most Recent Common Ancestor" (MRCA) is an estimate of how long ago a group of organisms could have had a single ancestor, whether measuring on the male or female side (or both). It is calculated through a measure of how diverse (through acquired mutations) a gene group is in a species versus how often mutations in a given area of the genome occur. Studies between species, such as chimpanzee and human, assume macro-evolution but other studies use measured mutation rates in the studied group, such as from grandfather to grandson.

In the case of humans, there is a wide range of dates, but the MRCA for Y-haplogroups (passed from father to son only) are at least 100,000 years in the past and may be double that. That is because there is an outlier, Y-haplogroup A00, which is different enough from the others so that it could have taken much more time for the mutations to arise between it and it's closest Y-Haplogroup kin (the other "A"s). Only a very few people from west Africa have this Y-Haplogroup. On the other hand, almost everyone in Eurasia is from a haplogroup of much more recent origin. Maybe 50,000 years or so.

Mothers pass mtDNA on to their daughters only. Thus it is a measure of female diversity sometimes called "mtDNA Eve." This measure is also at least 100,000 years old, with 150,000 years being the more recent estimate. 

These calculations are not just being made with humans. Here is a study which calculated the "Y-chromosome Adam" and "mtDNA Eve" for the great apes. It concluded that the "Y-chromosome Adam" for Chimps was over a million years ago- there is a lot of variety in Chimp Y-chromosomes. Not so gorillas, who had a coalescence time of 100,000 years. Less than humans unless you throw out the divergent A00 samples. 

These studies are deceptive for a number of reasons. In overall genetics I understand that humans are far less diverse than apes. Yet except for chimps, that study produced comparable numbers for MRCA for apes and humans. Yet comparing humans and apes in population genetics is comparing apples and oranges. We don't share the same recent history. Historical and near-historical times have been a period of massive expansion of humans. Except for one period of Y-chromosome loss around seven thousand years ago it is likely that few rare genetic variants have been lost in humans. The last 35,000 years have been prosperous ones for our species overall, and besides that on blip the last 10-12 thousand years have been spectacular.

With apes the record is the exact opposite. They have been driven to endangerment of extinction while humanity has been growing. Many minor Y-haplogroup types and mtDNA types which existed in these apes just a few thousand years ago are now probably extinct. Humans have lost some too, but overall humans have prospered so much that almost all Y-haplogroups around three thousand years ago are probably still around today and in greater numbers. Suppose Orangutans are driven to extinction (ignore those in captivity for this thought-experiment). When the last few families are left on a single island, the MRCA will be the great-grandpa of that small group of families. This explains why the graphic in the study (which I linked to above) shows that the Y-haplogroup "Adam" for Orangutans was only 200,000 years ago even if the species itself has been around longer. 

So the MRCA does not tell us anything about when a specific species came to exist. It could have come to exist long long before its measured MRCA. There could have been gorillas around long before 100,000 years ago even though the Y-chromosome MRCA , gorilla "Adam", was only 100,000 years ago.

The reverse is also true. A type of creature could also be much younger than its Y-haplogroup or mtDNA MRCA ("Adam" and "Eve). This is true under naturalistic evolutionary assumptions and it is also true under the most creationist assumptions of the Christ-centered model for early Genesis as described in the book.

The reason for this is that new types do not have to originate (with or without Divine help) from a single founding pair. A new type could begin from a population rather than a pair. And that population could start with more diversity than any one male and female founder. Thus calculations back to the time when there was only a single couple would be calculations back to the time of a fictional event. 

For example, suppose someone took a handful of Shih-tzus and bred them with a handful of Corgis. These are dog breeds developed in the recent past, perhaps the last 500-800 years. But each breed was developed from opposite ends of the dog family which goes back over 10,000 years. If this population crossed and produced a new hybrid breed, the hybrid would have greater diversity than either founding population (Shih-tzus or Corgis). It may have features identical to neither. It would be its own thing. The breed may not exist until this year. But if we ran DNA tests it would show the MRCA to be even further back in the past than the date that either parent breed was developed. That's because it would go back to the time when Corgis and Shih-tzus had a common ancestor, maybe 10,000 years ago. It would just look like the population spent most of its existence in an "extreme bottleneck". 

That's just what the human population looks like. The human mtDNA and Y-DNA seem to have a MRCA which goes at least 100,000 years in the past and 200,000 years might be a closer estimate. At the same time, we are all very similar in our nuclear DNA. It looks like our species had a long, long bottleneck. So the current belief is that Homo Sapiens spent most of its existence with a very small effective breeding population size of only 10,000 or less (note that if all individuals in this group are genetically super-alike the actual population size could be much larger than this). 

It isn't reasonable to think that we descend from a population that barely hung on for such vast stretches of time and then suddenly found a way to become the most common and dominant large animal on the planet. The simpler explanation is that, however we got here whether creation or evolution, we are a relatively recent arrival. Younger even than our Y-haplogroup and mtDNA MCRA date would indicate. 

The evidence indicates that whatever was walking around on two legs that looked something like us 150,000 years ago was still very different from us in how they acted, spoke, and perhaps in other ways. Whether this is because we are the evolutionary product of small segments of two hominid populations subsequently mixing and producing something new, or God creating something new in a small population of existing hominids, or even creating them anew with the barest of genetic information as a template, the bottom line is that there is no reason to think "humans" (in the sense of beings like us) go back to these calculated MRCA dates. Those dates can give a false picture. Beings like us were formed, by whatever means, when the evidence indicates that there were beings around who acted and thought like us. And that is much closer to 40K ago than 150K ago.

In conclusion, unless a species originated from a pair, MRCA for mtDNA and Y-haplogroups don't tell us anything about the origin of a species. They are just a measurement of time back to an event that never existed. This is because they could represent a time long after that species was formed (as with gorillas) or a time long before one was formed, as well may be the case with humans.

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(note: the Christ-centered model for early Genesis has humanity starting as a population and not just a single pair as it has people inside the Garden- Adam and Eve- and people outside the garden- whoever Cain was afraid of)

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