Everybody are Cousins to each other ?

Question

As there was a " genetic bottleneck " around 70000 years ago when Mount Toba erupted, only a few thousand people were left to colonise the world.

Would it be correct in reasoning that everyone on Earth is related to around 40 or 50th Cousins removed ?

Comments

We're all cousins, but it's not because of bottlenecks.  It's just because it takes two to tango.

40 generations is about Charlemagne, 50 is about 500 AD.

If you suppose that all the indigenous people of the Americas and the South Seas now have a trace of colonial European blood, 50-60 generations might be enough.

The usual estimates are higher, but I don't know what assumptions they make

https://en.wikipedia.org/wiki/Most_recent_common_ancestor#TMRCA_of_all_living_humans

Answer 1

The Toba Catastrophe Theory is controversial and not accepted by all scientists. See:

http://www.bbc.com/news/science-environment-22355515

https://en.wikipedia.org/wiki/Toba_catastrophe_theory#Genetic_bottleneck_theory

http://www.livescience.com/29130-toba-supervolcano-effects.html

However, for several reasons the genetic diversity of the human population has been low during different historic time periods. See:

http://rspb.royalsocietypublishing.org/content/early/2009/10/05/rspb.2009.1473

So, it is quite possible that all humans are related to some degree, as you suggest. Since there are a few clades and sub-clades in some genetic studies which are still represented by a single individual, the questions not yet answered are "is the present human population derived from a single source or from several?" and "from exactly what genetic precursor(s)?"

Comments

I'd think that we could get a good idea of how much real diversity there is by seeing how particular genes compare with those of chimpanzees.  I know that there's a high correlation, but probably there's more that can be found out in that line of research.

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In https://www.upf.edu/cexs/news/genetica.html we find the following quote:

What also became clear to the researchers was the complexity of the evolutionary history of chimpanzees in comparison with humans. The patterns of genetic diversity were consistent with a vast genetic flux or migration between ancestral populations with sudden expansions in population size, followed by accidents.

"Humans", conversely, "have a relatively simple evolutionary history", say the authors. "It is clear that in the last few million years chimpanzee populations fluctuated enormously in size and complexity." The basis of these population collapses is clear but it coincides, in part, with a period of time in which the human population began to prosper.

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Last few million years?  There have been many species of humans in that time.  We can hardly guess at their evolutionary history.

Homo sapiens has shared the planet with other human species for most of its history.  Which we can't get our heads round at all.  They probably interbred.

If our genes are simple now it's because we're the only survivors of recent bottlenecks.