What is MRUGA vs. IAP vs. nearly IAP?

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Dear Dr Swamidass,

I just finished reading your captivating book ‘The Genealogical Adam and Eve’. I thoroughly enjoyed it, and it helped provide some clarity regarding those enigmatic first few chapters of Genesis and the many ways in which it can be viewed, however I just have one question. Although I understood most of the book, there was one thing that was not clear to me. Would you be able to provide a delineation between the most recent universal common ancestor (MRUGA), the identical ancestor point (IAP) and the near identical ancestor point (I think you called it ‘NIAP’)?

You mention “Going back a little bit further we reach the identical ancestor point (IAP), where everyone at that point and more ancient is either the ancestor of everyone alive to day or the ancestor of nobody”. Do you mean that at the IAP, 100% of people are the ancestors of everybody, or 100% of people are the ancestors of nobody? If so, what does that mean? Or do you mean that at of everyone alive at the IAP (100% of people alive at that point), some of those people are the universal ancestors of everybody alive today (lets arbitrarily say 63%), and the remaining 37% of people at that point are not universal ancestors? If so, what does that mean? And how then does the NIAP relate? Is the IAP the period there everybody at that point (100% of people) are the universal ancestor of the MRUGA? If so, could you explain that more?

You also mention certain IAP individuals are ‘poorly located’ and ‘unlucky’. Please could you explain this more? I get that those people are in the most isolated regions of the globe, but how are they poorly located and unlucky in regard to the IAP?

Lastly, I am assuming your Adam (and Eve) would be the MRUGA, and not the IAP, right? Could you explain this a little more? Perhaps in your explanation regarding these questions, you could provide some theoretical examples to help facilitate understanding.

I thought your explanations were very clear throughout the rest of the entire book, and have already recommended it to numerous other people – it’s just this one thing I was uncertain about. I know you go into more detail as to what these terms mean. I understood the individual explanations, but just failed to see how they all related.

Any help you could provide me with would be greatly appreciated.

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Hello @Liam. Welcome to the forum. Tell us a bit about yourself?

Some Relevant Quotes

They key text is on p. 59,

The recent end of the range is defined by three critical dates: (1) the most recent universal genealogical ancestor (MRUGA), (2) the nearly identical ancestor point (nearly IAP), and (3) the identical ancestor point (IAP). The most recent date is that of the MRUGA, the first point. Here, the first universal genealogical ancestors appear somewhere in the globe. The most ancient date is that of the IAP, the third point. Here, each one that leaves any ancestors is also a universal ancestor. The only people at this point who are not universal ancestors are those who leave no surviving descendants. Between these two dates is the nearly IAP, where nearly everyone alive (95–99 percent) who leaves ancestors is also a universal ancestor.

And this sentence is important too (p. 57)

Second, the estimates so far are for the most recent of all universal ancestors. This is a tiny number of individuals, possibly in specific areas of the globe, and only arising at some narrow window of time in the past. It would be almost inconceivably lucky for Adam and Eve to be part of this tiny group of people. Nothing in our hypothesis, however, requires them to be the most recent.

In the PSCF paper, and the book, I depict it like this:

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The Questions

I mean that at the IAP, everyone either is ancestor of everyone or is ancestor of no one. Most people are ancestor of everyone.

In this case, not everyone, but most people, are either ancestor of everyone or are ancestor of no one. There would be a small group of our ancestors (perhaps %1) that are only ancestors of some people today.

If they were born in Australia or the Southern tip of South America, they are on the outer-reaches of the map. It would take longer for them to become a universal ancestor. That would be poorly located.

If, by chance, none of their descendents migrated far for several centuries, it would take them longer to become a universal ancestor. That would be unlucky.

In this case, I mean unlucky and poorly located merely in reference to the speed at which they become universal ancestors. It would take them a longer time than most others.

No. I’m pretty clear we do NOT expect Adam and Eve to be at the MRUGA. See the quote above. “Nothing in our hypothesis, however, requires them to be the most recent.”

Great questions. I hope that helps!

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Thanks for your response. I still need to do a little more thinking on this, but you’ve certainly provided more clarity

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