lpetrich

I have a problem with the hypothesis of volcano-caused near-extinction. It is that our species has distinguished itself by being able to live in a wide variety of environments -- even with Paleolithic technology. So would our ancestors back then have been very vulnerable to something that produced little evidence of mass extinctions?

ps418:
There was no speciation event, but there was big change in the complexity of cultural artifacts around 50k years BP, though obviously that could not have lead to a major reduction in genetic diversity at 70k years BP. Maybe the cultural revolution began earlier than 50k years BP or the reduction in genetic diversity happened later than 70k years BP.

The next questions are: where and when was this complexity change? When did it happen in Africa as opposed to (say) Europe? I think that this change could qualify as marking the emergence of a new species.

contracycle

Fair amount of evidence for coastal-dewelling humanoids in sub-saharahn africa. Not sure on the mechanics, but possibly a tsunami effect would be disproportionately effective to beach-combers.

mark24

Ipetrich,

I have to take issue with you here. Modern humans are thought to have been around for 30,000 years before the bottleneck anyway, plus there there is no evidence of 1/cladogenesis at that time, & 2/rapid evolution following cladogenesis.

In fact, PE suffers from having no unequivocal evidence at all. The best adherents of PE can do is point to periods of stasis. The problem being that there is ample evidence of changes in tempo of evolution within a lineage followed & preceded by stasis. Yet none of the rapid tempo can be associated with cladogenesis, which is required for it to be evidence of PE.

PE should be put back on the shelf labelled "awaiting evidence".

Mark

Oolon Colluphid

Well Mark, I'm the last person you'll normally find defending punk eek, but that's a slight overstatement. Only slight, admittedly, but still...

See the SciAm item Score One for Punk Eek.

Cheers, Oolon

Jimmy Davies

We know that a 100,000 years ago, in South Africa, men GENETICALLY identical to modern me, in other words, they were modern men, left their fossil evidence.

Now some genius scientists are going to tell us that 30,000 years later the human race was reduced to a mere 2000 individuals by environmental stress and we almost didn't make it?

Tell you what, I was in the rez Indian hospital waiting room once, into the emergency room comes a guy, got drunk with his buddies, they got riled at one another, and so his buddy buried a hand axe in his skull and pushed him off the bridge into a dry riverbed full of hard rocks. Guy walked half a mile up to the hospital axe still stuck in his head laughing and joking about it all---and his jokes were funny.

These scientists are telling us this guy is gonna spend 30,000 years struggling marginally to exist? Give me a break. Take those boys from 100,000 years ago, give them a few days of instruction and they'll kick the ass of these scientists in Chess, steal their girlfriends, too.

Even the knotheads came up with that anal theory would have never been close to extinction had they been back 70,000 years ago.

Rhaedas

"Environmental stress" can mean anything from a bad crop season or hot weather, to a catastrophic event. Your objection and example are actually supportive to the idea, showing that even dropped to such a low number by something, humans survived and prevailed, to expand across the globe.

Something similiar seems to have happened to the cheetah as well, only the numbers dropped too low for genetic diversity (something like only 12-20 at one time?), and affect their survival (in addition to man's influence to their numbers).

At some point all species have been/are threatened with survival or extinction. Most don't survive...

Jimmy Davies

Hi Rhaedas. Most species don't survive, almost a 100% percent of all that has lived on this ball of dirt are dead. Thank goodness some got lucky or none of this would be here.

Part of your post is illogical. The point of the theory was that mankind almost went extinct. My theory is bullshit he almost did. Citing the fact he almost went extinct because he was down to 2000 individuals but was too resilient to go extinct, MEANS he didn't almost go extinct! And I seriously question the 2000 individual count. The fossil record is so spotty, we can't hardly find squat enough to keep the creationist looneys at bay, but next thing you know one of these geniuses will be trying to ebay off Fred Flintstone's bowling ball, claiming it was in sutu and had been accurately carbon dated.

mark24

Oolon,

Thanks for the link! It is a seeerious stretch to call this evidence of PE, & is certainly not unequivocal. Given that these are asexually reproducing bacteria that are specially selected for their inability to recombine genetic material, we are essentially looking at single lineages rather than sexually reproducing (& therefore recombining) populations that PE was intended to represent.

This simply shows how fast a mutation can benefit it's host lineage (in an asexual bacteria), by outcompeting its own species & becoming fixed. There is no true cladogenesis in the sexually reproducing species sense. In fact I could argue that this is better evidence of an anagenetic rather than cladogenetic tempo increase.

Mark

contracycle

Which part of "almost" did you no understand?

Jimmy Davies

I see you have the same problems with logic the other fella did. Let me put it in VERY simple terms for you---the number of humans is irrelevant. Since their survival defines their resilience, they didn't ALMOST go extinct. This is a common one with illogical people, they start from a premise acknowledged as fact and then judge the merit of drawn conclusions on this arbitrarily imposed value.

Work harder using your own noggin. This ain't rocket science.

Now, what part of illogical don't you
understand?