As someone has already pointed out, no apes have tails, which not only makes the question of choosing any particular 'homo' species quite poor, but it also brings into question the rest of the question in the OP.
Monkeys have tails, so the idea that those tails provide a useful advantage by providing balance for larger animals does not seem to be correct either. This is not a complete answer thought, because many large animals do have tails that serve non balancing functions like swatting flies.
And why is natural selection eliminated as an answer. My guess is that mram10 really wants to explore what the factors are that might make not having a tail advantageous. I am rejecting more negative guesses that do not reflect well on the OP.
I would suggest that tails on apes/monkeys are not a huge advantage for monkey/apes not primarily living in trees, so a deleterious mutation that resulted in those animals losing their tails after they had changed to a life style living below trees would not be only slightly deleterious. Tails do interfere with sitting down so maybe there was a slight advantage. So perhaps a combination of natural selection and drift is the explanation.
At any rate a quick search on google turned up a link to this paper, whose abstract seems to propose an explanation that might just as well be in Sanskrit for me. I have no idea what they are talking about.
Mutational tail loss is an evolutionary mechanism for liberating marapsins and other type I serine proteases from transmembrane anchors - PubMed
ABE:
I see this question in another thread: "Where did natural selection get it's intelligence?", so perhaps I am giving mram too much credit.
Edited by NoNukes, : No reason given.
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