What makes us evolve? Extinction level events and big environmental changes. Basically pressure, like many others have hinted at.
Where does this pressure come from? Well, we have been in an ice age for the past 2.5 million years. It's no coincidence that it is almost the exact
time frame for the development of the homo genus.
Ice ages basically go in cycles bouncing from warm to cold and this has been happening since this particular ice age began. Right now we are still in
an ice age, but are in an interglacial period (period of warmth).
Here's the time line. The years aren't exact, they averages.
The last glacial period lasted from 110,000 years ago until about 12,000 years ago. Homo sapiens are the only hominid survivors of that period.
Prior to 70,000 years ago, Neanderthal, Denisovans, Homo erectus and Homo sapiens all coexisted. Basically this shows me that Homo sapiens survived
this period while the others did not. It is natural selection in action. Neanderthals and Denisovans disappeared around 30-40k years ago. The
glacial maximum during that period was around 26,000 years ago. It seems like their extinction is way too close to this period to be coincidence. I
firmly believe homo sapien ingenuity is what propelled us, while the others bit the dust.
Prior to the last glacial period, we had another warm period that ranged from about 115-130k years. Compared to the ice age, that is a very short
Before that we had another glacial period that went from about 200-130k years ago. Around 200,000 years ago is coincidentally right near where we
find the oldest homo sapien fossils, and right around when Homo Heidelbergensis went extinct. So another species goes extinct during the glacial
200,000 - 240,000: Interglacial with a mini cooling spike right in the middle. Another short warm period, likely the period when late
heidelbergensis transitioned to homo sapien.
240,000 - 300,000: Glacial period. This is the period where Neanderthal likely split off from Heidlebergenesis and also the beginning is right around
where the earliest homo rhodensiensis fossils are seen.
300,000 - 330,000: Interglacial.
330,000 - 375,000: Glacial.
375,00 - 425,000: Interglacial.
This chart shows the last 450,000 years.
If you go back to the beginning of the entire ice age around 2.5 years ago, you start to see the homo genus take over and then slowly but surely the
intellect begins steadily increasing. The homo genus began in the years leading up to the ice age and then took off. I believe that the
interglacial periods are generally the times when genetic diversity increases and that the glacial periods (or transitions between glacial /
interglacial) are when the majority of selection events and extinctions occur.
So for humans and human ancestors I firmly believe that the bouncing back between warm and cold is what led them to step beyond the rest in intellect
and ingenuity. It was heavy environmental pressure bouncing between extremes in temperature. This is also favorable to create diversity in a
relatively short time. I see the correlation, although the details are still a bit fuzzy and there is certainly way more to the picture than JUST the
temperatures, but it seems to play a heavy role, especially when considering the environmental pressure caused by the transitional periods which
likely displaced many various hominids into differing environments, to which they adapted accordingly.
edit on 26-8-2015 by Barcs because: (no reason given)