A whole bunch of media reports seemed to imply some scientists proved Adam & Eve or Noah’s Ark. The headlines read, “Did a mysterious extinction event precede Adam and Eve?” (Fox), “All humans are descended from just TWO people and a catastrophic event almost wiped out ALL species 100,000 years ago” (Daily Mail), or “Turns out all of humanity is related to a single couple” (NY Post). However, this research on Mitochondrial Eve does not mean what many people assumed: it does not prove Biblical stories.
Let’s review the coverage by the Daily Mail:
All modern humans descended from a solitary pair who lived 100,000 to 200,000 years ago, scientists say.
Scientists surveyed the genetic ‘bar codes’ of five million animals – including humans – from 100,000 different species and deduced that we sprang from a single pair of adults [each species came from a single female] after a catastrophic event almost wiped out the human race [pure speculation without evidence as we have 46 other bits of DNA, most of which likely don’t come directly from that woman]. […]
Stoeckle and Thaler, the scientists who headed the study, concluded that ninety percent of all animal species alive today come from parents that all began giving birth at roughly the same time, [it’s 100-230,000 years so very “roughly”] less than 250 thousand years ago – throwing into doubt the patterns of human evolution [not really].
The Actual Study
The study looked at mitochondrial DNA, the DNA outside the nucleus that we all inherit from our mom alone. (My sister’s daughter would have the same mitochondrial DNA as my mom [her grandma].)
The new study, “Why should mitochondria define species?” relies largely on the accumulation of more than 5 million mitochondrial barcodes from more than 100,000 animal species, assembled by scientists worldwide over the past 15 years in the open access GenBank database maintained by the US National Center for Biotechnology Information. […]
And the basic result was:
“One might have thought that, due to their high population numbers and wide geographic distribution, humans might have led to greater genetic diversity than other animal species,” he adds. “At least for mitochondrial DNA, humans turn out to be low to average in genetic diversity.”
“Experts have interpreted low genetic variation among living humans as a result of our recent expansion from a small population in which a sequence from one mother became the ancestor for all modern human mitochondrial sequences,” says Dr. Thaler.
So basically, all human mitochondrial DNA comes from one female 100-230,000 years ago. We have such a wide range for the time frame because it is based on the estimated rate of random genetic changes. The main point this study found is that most species – no matter the population, have about the same variation in mitochondrial DNA when species with larger populations were expected to have more variety.
The Way DNA is Passed Down
It is important to put this into context. Just because one of the 47 bits of DNA (46 chromosomes and mitochondrial) in our bodies all came from a single couple, doesn’t mean anything about the other 46 bits did. Let me explain this by a concrete example. I have three sisters and no brothers. Thus, since I am a celibate priest, my dad’s Y-chromosome got passed down to me and hit a dead end. That piece of his DNA won’t be transferred to any other humans ever. Nonetheless, my dad has six grandkids who probably got a good portion of their other 45 chromosomes from him. On the other hand, one of my brothers-in-law has brothers but no sisters, so his mom’s mitochondrial DNA also hit a dead end. We have known that things like this happen and certain genes from certain individuals hit dead ends while others proliferate.
Mitochondrial Eve and Y-Chromosnal Adam
All this study is showing is that 1 part out of 47 can be traced back to one woman. This has been known for years and there is even a Wikipedia page for “Mitochondrial Eve” with 95 citations between footnotes and further reading. Likewise, there is “Y-Chromosomal Adam” from which all men get our Y-Chromosome. These two likely lived at different times and places: if we average the current estimates, Y-Chromosnal Adam lived about 75,000 years before Mitochondrial Eve.
The other 45 bits of DNA get mixed up far more often and can be passed down from either parent, so it is harder to trace back variations.
Mitochondrial Eve is not even the first human. Smithsonian quotes Roger Bull, a senior research assistant in the molecular biodiversity lab at the Canadian Museum of Nature, who did a research project to discover the whale Mitochondrial Eve. Bull states, “The use of the term was a misinterpretation, given that the research was about the most recent common mitochondrial ancestor of all living humans … not about the first human woman ever.”
Wikipedia provides a chart that may help. You can see how Mitochondrial Eve is the common female ancestor of all current individuals, but not the first woman. (Color indicates which strand of mitochondrial DNA was passed down.)
Don’t Misread Science
People today tend to have a strong belief in science. To evangelize, we need a credible Church. I think that part of making the Church credible today is properly understanding science and integrating it with faith. When I worked with teens, the intercession between science and faith was one of the top questions. We shouldn’t jump on a scienctific study that seems to be in line with faith, without ding a little critical work to understand what is being said. We should avoid looking overly credulous.
In this case, what is being said is not that there was Noah’s ark or a garden of Eden. What is being said is that certain parts of DNA proliferate within a species and we can trace one of the 47 parts back to a single woman 100-230,000 years ago. Other animals are likewise. The surprise finding of this study was that the variations were similar independent of how many members of that species there are (100,000 sandpipers vs. 500,000,000 sparrows), which was contrary to what was expected.
The Church’s Judgement
What we do know is that humans came from a single original couple, the real first humans, Adam and Eve. After saying we can study evolution, Pius XII stated:
For the faithful cannot embrace that opinion which maintains that either after Adam there existed on this earth true men who did not take their origin through natural generation from him as from the first parent of all, or that Adam represents a certain number of first parents. Now it is in no way apparent how such an opinion can be reconciled with that which the sources of revealed truth and the documents of the Teaching Authority of the Church propose with regard to original sin, which proceeds from a sin actually committed by an individual Adam and which, through generation, is passed on to all and is in everyone as his own.
Science will never contradict the faith. But that doesn’t mean science will prove the faith. Science and faith both lead us to the truth by different paths.