Comments on: Graphs, trees, and origins of humanity http://igoro.com/archive/graphs-trees-and-origins-of-humanity/ On programming, technology, and random things of interest Fri, 11 May 2012 19:47:05 +0000 hourly 1 http://wordpress.org/?v=3.1 By: Igor Ostrovsky http://igoro.com/archive/graphs-trees-and-origins-of-humanity/comment-page-1/#comment-2624 Igor Ostrovsky Mon, 04 Apr 2011 23:50:39 +0000 http://igoro.com/?p=621#comment-2624 [Edit: nevermind, I misread "all-but-finitely-many" as "finitely many"] <del datetime="2011-04-05T00:04:11+00:00">Xamuel: I don't follow. Mitochondrial Eve is an (non-unique) ancestor to all people alive today. So, only a finite number of people will ever exist that were not descended from Eve. In order for X to be infinite, an infinite number of Eve's descendants must be in X. Then clearly also Eve must be in X. But then Eve is an ancestor to infinitely many members of X, which contradicts (2).</del> [Edit: nevermind, I misread "all-but-finitely-many" as "finitely many"]

Xamuel: I don’t follow. Mitochondrial Eve is an (non-unique) ancestor to all people alive today. So, only a finite number of people will ever exist that were not descended from Eve.

In order for X to be infinite, an infinite number of Eve’s descendants must be in X. Then clearly also Eve must be in X.

But then Eve is an ancestor to infinitely many members of X, which contradicts (2).

]]> By: Xamuel http://igoro.com/archive/graphs-trees-and-origins-of-humanity/comment-page-1/#comment-2623 Xamuel Mon, 04 Apr 2011 23:20:10 +0000 http://igoro.com/?p=621#comment-2623 Hi Igor. You might be interested in the following theorem, which I've submitted to the journal Cladistics and is awaiting peer review right now. Assume mankind doesn't go extinct; that everyone has one male parent and one female parent; that mankind traces back to one ultimate pair of ancestors; and that no individual has infinitely many children. Then: there is an infinite subset X of people such that 1. every parent of a person in X is also in X, and 2. every member of X is an ancestor of all-but-finitely-many of the members of X. Hi Igor. You might be interested in the following theorem, which I’ve submitted to the journal Cladistics and is awaiting peer review right now. Assume mankind doesn’t go extinct; that everyone has one male parent and one female parent; that mankind traces back to one ultimate pair of ancestors; and that no individual has infinitely many children. Then: there is an infinite subset X of people such that 1. every parent of a person in X is also in X, and 2. every member of X is an ancestor of all-but-finitely-many of the members of X.

]]> By: Igor Ostrovsky http://igoro.com/archive/graphs-trees-and-origins-of-humanity/comment-page-1/#comment-1029 Igor Ostrovsky Fri, 23 Jul 2010 05:25:02 +0000 http://igoro.com/?p=621#comment-1029 OK, I rephrased it: <blockquote>This simulation is not a sophisticated model of a human population, but it is <del datetime="2010-07-23T05:25:42+00:00">not an awful one either</del> sufficient for the purposes of illustrating genetic drift.</blockquote> Is that better? :) OK, I rephrased it:

This simulation is not a sophisticated model of a human population, but it is not an awful one either sufficient for the purposes of illustrating genetic drift.

Is that better? :)

]]> By: Alexey Romanov http://igoro.com/archive/graphs-trees-and-origins-of-humanity/comment-page-1/#comment-1028 Alexey Romanov Fri, 23 Jul 2010 04:52:58 +0000 http://igoro.com/?p=621#comment-1028 > But, a constant population size is not a requirement for genetic drift. Certainly it isn't. But it does disqualify the model from being "not an awful one". > But, a constant population size is not a requirement for genetic drift.

Certainly it isn’t. But it does disqualify the model from being “not an awful one”.

]]> By: Igor Ostrovsky http://igoro.com/archive/graphs-trees-and-origins-of-humanity/comment-page-1/#comment-1027 Igor Ostrovsky Thu, 22 Jul 2010 21:06:03 +0000 http://igoro.com/?p=621#comment-1027 My greatly simplified example does assume a constant population size. But, a constant population size is not a requirement for genetic drift. Besides, the human population fluctuated in the past, sometimes dropping to <a href="http://en.wikipedia.org/wiki/Population_bottleneck" rel="nofollow">small numbers.</a> For example, roughly 70,000 years ago, the human population may have dropped down to thousands of individuals (<a href="http://en.wikipedia.org/wiki/Toba_catastrophe_theory" rel="nofollow">1</a>, <a href="https://genographic.nationalgeographic.com/genographic/dawn.html" rel="nofollow">2</a>). I'll add a clarification to the article, since the same point was raised on Hacker News and reddit as well. My greatly simplified example does assume a constant population size. But, a constant population size is not a requirement for genetic drift.

Besides, the human population fluctuated in the past, sometimes dropping to small numbers. For example, roughly 70,000 years ago, the human population may have dropped down to thousands of individuals (1, 2).

I’ll add a clarification to the article, since the same point was raised on Hacker News and reddit as well.

]]> By: Anonymous http://igoro.com/archive/graphs-trees-and-origins-of-humanity/comment-page-1/#comment-1026 Anonymous Thu, 22 Jul 2010 20:50:47 +0000 http://igoro.com/?p=621#comment-1026 This model assumes that the population size is constant. This model assumes that the population size is constant.

]]> By: James http://igoro.com/archive/graphs-trees-and-origins-of-humanity/comment-page-1/#comment-1025 James Thu, 22 Jul 2010 09:11:13 +0000 http://igoro.com/?p=621#comment-1025 Excellent. Really interesting, well-written article! Excellent. Really interesting, well-written article!

]]>