Re: [Fwd: Earth Battered Through History By Comets]
Wed, 25 Aug 1999 20:02:23 +0000

Hi Gary,

At 09:19 AM 08/25/1999 +0100, Gary Collins wrote:
>Can't say I do, no. But then I wouldn't expect to, it's not something I've
>studied. If *you* don't, then that's far more significant.

Not necessarily.

What struck me
>as odd is that if this hypothesis is true, why has it taken so long to come
>to light. Perhaps because of lack of craters, as you suggest. It was
>reported in what I hope would be a fairly reliable source - NASA news,
>I think it was - so I guessed it should at least be something not too
>unreasonable. As I said, I haven't yet had time to look at the article
>itself, I should be able to do that today.
>What was on my mind though was something I vaguely remember
>reading about genetic studies - mtDNA I think it was, though I'm not
>entirely sure - which mentioned a surprising lack of diversity in humans
>as opposed to apes, and suggesting a more recent divergence than
>usually believed. If something like comet/asteroid collision, or indeed
>any natural disaster, like volcanoes as Kevin suggested, did occur,
>maybe more than once, and reduce the population significantly, this
>would explain the discrepancy. (This is probably old hat, anyway!)

ACtually the lack of mtDNA diversity has a number of competing hypotheses
to explain our lack of diveristy compared with chimp diversity. One is the
mitochondrial Eve view. Another is that there is a selection which
maintains a lack of diversity. Some have suggested that since mitochondria
provide energy for the cells and since humans have a big brain that is a
huge consumer of energy, only mitochondria which are exceptionally
efficient are capable of fueling our brains. This would result in
selection getting rid of non-efficient mtDNA and limiting our diversity.


Foundation, Fall and Flood
Adam, Apes and Anthropology

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