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How do we know we are all Homo Sapiens?

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pstotto
1370074.  Tue Dec 29, 2020 2:25 pm Reply with quote

How do we know we are all homo sapiens, when there are 7 billion people and only an infinitesimal amount of those people have had DNA tests?

 
crissdee
1370081.  Tue Dec 29, 2020 3:43 pm Reply with quote

Quite apart from the fact that such DNA tests as have been done have already revealed a rather stronger presence of Neanderthal DNA than was previously thought, what else do you imagine we might be?

While I agree that nothing like 7 billion people have been tested, I would suggest that the proportion, by now, might be more than "infintesimal".

 
pstotto
1370084.  Tue Dec 29, 2020 4:12 pm Reply with quote

I know someone who looks exactly like a Baboon.

How many people do you think have been tested for DNA in the world today?

Less than a million?

That's still a tiny fraction.

 
crissdee
1370092.  Tue Dec 29, 2020 5:21 pm Reply with quote

It actually wouldn't surprise me that much to find that well over a million people have had DNA tests done by now. It is a regular feature of police investigations across the Western world, and much the same for medical purposes. You can send for kits through the post now, for nothing more important than idle curiosity. The police are not of course looking for your genetic heritage, just to see if you were the suspicious character outside Barclay's last Wednesday, but the test is done, and the information recorded.

I admit that even two million is a tiny fraction of the world population, but (imho) more than infinitesimal. People play the lottery against odds a thousand times longer...

 
ali
1370094.  Tue Dec 29, 2020 5:37 pm Reply with quote

According to this 2019 article, more than 26 million people have taken a DNA test from one or other of the genealogy companies.

 
crissdee
1370097.  Tue Dec 29, 2020 5:44 pm Reply with quote

So we are talking now about a reasonable fraction of the population, 1 in about 270 if my maths is any good.

Once again. pstotto's theorizing falls to pieces when confronted with real world data.

 
pstotto
1370099.  Tue Dec 29, 2020 5:56 pm Reply with quote

:-)

We are all Homo Sapiens according to an analysis of 0.0037037037%

of possible results?

Scientific method???????

 
PDR
1370111.  Tue Dec 29, 2020 8:35 pm Reply with quote

I'm afraid it's a non-intuitive piece of probability theory.

If you have a reasonably diverse or "random" sample of 26 million then the probability that this sample does not represent the population at a reasonably meaningful discrimination ratio is rather small regardless of the size of the population. If you were looking at a continuous distribution (some variable attribute) then increasing the sample size would slowly increase the precision (improve the discrimination ratio) but the null hypothesis we have here is a simple discrete distribution with two values "yes" and "no". A diverse sample of a few hundred (or even a few dozen) would be enough to give a reasonably confident answer to that. The point being that the diversity within the sample is far more significant than the number of data.

To understand why this is so the starting point is to consider what would make the next randomly-selected sample UNrepresentative - what is the probability that the dozen you have selected are a special case, and why.

PDR

 
ali
1370113.  Tue Dec 29, 2020 9:37 pm Reply with quote

pstotto wrote:
:-)

We are all Homo Sapiens according to an analysis of 0.0037037037%

of possible results?

Scientific method???????


0.37%-ish actually, which is a perfectly reasonable sample size (though I would question whether a self-selecting group such as customers of online genealogists was truly representative).

 
Celebaelin
1370114.  Tue Dec 29, 2020 10:42 pm Reply with quote

Humans are unique in the extant Hominidae in (usually) having 23 chromosome pairs; the number of people thus tested is not known but it's big and exceptions are found only in genetic disorders which predispose towards infertility*.

https://en.wikipedia.org/wiki/Chromosome_2#Evolution

Do you want to debate what constitutes being human (i.e. Homo sapiens)? To my mind being an member of the family Hominidae with 23 chromosomes, and/or being the offspring of two such, is the way to go with it. OTOH conforming to a given set of anatomical features is an accepted methodology in paleoanthropology while still other definitions tend towards some faculty or faculties of a living brain implying that you would cease to be human if you lost, or never attained, certain mental faculties yet were still alive and would definitely no longer be human if you were dead.

As yet no definition of human that I'm aware of depends on any degree of conformity to a known sequence of shared genetic code.

* there are no absolutes in this regard AFAIK as 'processing errors' could on rare occasions create viable gametes


Last edited by Celebaelin on Wed Dec 30, 2020 11:01 pm; edited 2 times in total

 
Alfred E Neuman
1370121.  Wed Dec 30, 2020 4:11 am Reply with quote

pstotto wrote:
I know someone who looks exactly like a Baboon.

Perhaps you just need a new razor?

 
pstotto
1370140.  Wed Dec 30, 2020 7:13 am Reply with quote

Sounds like you're giving away your own idea of yourself when you look in the mirror unshaven, Alf.

If we're talking probability then what about immigration?

40% corruption there, a 100 come through Heathrow, 40 criminals let into the country to cause mayhem in Uxbridge or wherever.

 
PDR
1370145.  Wed Dec 30, 2020 8:20 am Reply with quote

I believe the point is illustrated - we only needed to see a sample of one post to identify (at the 99.99% confidence interval) a gibbering racist twat.

PDR

 
Jenny
1370156.  Wed Dec 30, 2020 10:37 am Reply with quote

How random is that sample though? I think it likely that the vast majority of that 26 million will be people from more affluent and developed countries.

Not that I think pstotto's speculation that not all people are homo sapiens stands up to scrutiny, but the randomness of the sample might be an area worth examining.

 
pstotto
1370158.  Wed Dec 30, 2020 10:50 am Reply with quote

PDR identifies himself as a racist upon a personal presumption of his, based upon an imagined country of immigrant origin where there is 40% corruption.

Jenny, a 0.37% sample of a barrel of ale is not the same as a 0.37% apprehension of the human race, surely.

 

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