faetal on 8/11/2016 at 10:00

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Like I say, I agree with you 95%, but I think that with the fossil record you have to consider some very fine points:

1) How many offspring were the survivors having in general?

2) How many years of care do those offspring require before they are able to fend for themselves?

3) How metabolically demanding are those species?

Because humans have about the lowest possible number of offspring ever, are born under-developed to maximise brain size without rendering female pelvises useless for load-bearing, meaning that humans can't contribute to much for years and create a burden which the other humans have to bear, plus we require resource abundance as our brains are glucose sponges and bipedal movement is way less energy efficient versus quadrupeds (that is something you can certainly trump me on, so if I'm wrong, I'll concede without hesitation), meaning we need more resources in to support growth versus pretty much anything else. Of course there are ways around it, but since our history only includes abundance, we don't have much of a read on how much the expense of our development factors into a loooong (say thousands of years) period of scarcity. Bearing in mind that scarcity needn't mean desert, it could just mean a massive upsurge in weedy species which we find it difficult to get good nourishment from. Think about how many humans die of starvation per year, even with the abundance we have.

Do you think it's implausible, or just unlikely? Because I'm not disagreeing with the latter.

faetal on 8/11/2016 at 10:17

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I'mm envisaging the possible of a scenario where our technological leanings aren't enough to compensate for the shortfall in our biological ones. In this era's ecological conditions, it has been enough to propel us to the stars, but a big enough change could see our tech ability just as a means to slow down our eventual extinction rather than completely overcome it.
I'm a molecular biologist, I see everything as competing equilibrium equations - in my 5%* scenario, I'm thinking (unfavourable conditions - tech amelioration) * time, may not lead to survival.

I'm surprised about the legs thing, since the largest part of land-based evolution seems to have been based around quadrupedal movement until very late on. I always assumed we traded mechanical efficiency for being able so see over tall grass and having the use of our hands. But then, I guess, Usain Bolt, so...

* I keep using 5% / 95%, just to illustrate that I'm talking only worst case scenarios.

nickie on 8/11/2016 at 10:27

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We also have a paleoanthropologist here who taught me everything I know about bipedalism of which I remember absolutely nothing much at all. I shall point him in the direction of this thread and/or dig out the emails.

Starker on 8/11/2016 at 10:28

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That's not because we don't have enough food to go around, though. From the perspective of producing enough calories to meet the needs of the world population we have more than enough. It's in large part because of uneven distribution that leads to some places having too much food and some places having too little, hence we have people starving to death in one place and people dying from obesity in another. USA, for example, throws away something like 30-50% of its produce: (https://www.theguardian.com/environment/2016/jul/13/us-food-waste-ugly-fruit-vegetables-perfect)

Starker on 8/11/2016 at 10:38

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We have means to preserve food, though.