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I proposed this as a non-joke explanation a while back.
Thread incoming
1/x https://twitter.com/mtpollack/status/1275074760070684676
Thread incoming
1/x https://twitter.com/mtpollack/status/1275074760070684676
Mapping Earth as a graph with continents as nodes and connections as edges from a human migration perspective Earth looks like this
Africa
|
Eurasia
/ \\
Americas Oceania
2/x
Africa
|
Eurasia
/ \\
Americas Oceania
2/x
Spaceflight capable intelligence is almost certainly not going to develop on the continent of origin; intelligence is an adaptation that has to give fitness returns in exchange for the biological cost of larger brains and slower time to maturity
Why not?
3/x
Why not?
3/x
On the continent of origin everything there is evolutionarily linked - all in an arms race. The intelligent species wants to eat everything to turn it into biomass and the microscopic parasites want to crack that single species' immune system to convert that biomass
Result?
4/x
Result?
4/x
Equilibrium - strong selective filter on the immune system, strong filter to mix it up with lots of children with slightly different immune systems to beat the parasites. On the other hand, can't beat the animals who you're unintentionally breeding to be wise to your tricks.
5/x
5/x
You can stick in that state until the star engulfs the planet.
Contrast with what happens when the species moves to an open continent with seasonal variation.
6/x
Contrast with what happens when the species moves to an open continent with seasonal variation.
6/x
Everyone is familiar with the "cold winters" hypothesis of intelligence and it's almost certainly true to some extent (neanderthals did have larger brains ~1410 cm^3) - that's definitive proof of selective pressure
7/x
7/x
Ok, so go back to that graph - this species moves out of the continent of origin to the one continent it's linked to, spreads out across it, discovers lots of animals with generations of selection for things that aren't "can survive human predation"
Result?
8/x
Result?
8/x
Rapid conversion of biomass from large herbivores to humans - mass extinctions of large animals of all kinds.
Uh oh. That's a lot of biomass of humans that don't have their prior food source.
What's the next step?
9/x
Uh oh. That's a lot of biomass of humans that don't have their prior food source.
What's the next step?
9/x
Speculation but probably a huge die off in humans as fewer bands survived - those that branched off earlier and started doing weird stuff like controlling the breeding of prey animals and protecting them as you use them to convert all the uneaten vegetation to milk and meat
10/x
10/x
Now another race is on because that tribe over on the next hill might be successfully protecting sheep from wolves but the men of your tribe are more clever than wolves.
Homō hominī lupus est
Why stop at taking the sheep though?
Why not take the women too?
11/x
Homō hominī lupus est
Why stop at taking the sheep though?
Why not take the women too?
11/x
The "total Y chromosome replacement event" stage begins.
By the nature of humans evolution for conflict isn't evolving bigger claws or teeth or thicker hide; it's evolving the ability for men to cooperate more successfully in a war band.
12/x
By the nature of humans evolution for conflict isn't evolving bigger claws or teeth or thicker hide; it's evolving the ability for men to cooperate more successfully in a war band.
12/x
More successfully than what? The men you're raiding.
They're under the same pressure. Bam! The most powerful evolutionary force has been unleashed - the arms race. In this case the arms race is for cooperation.
Eventually the land gets filled to capacity of herders
13/x
They're under the same pressure. Bam! The most powerful evolutionary force has been unleashed - the arms race. In this case the arms race is for cooperation.
Eventually the land gets filled to capacity of herders
13/x
Next step? You can pack in people more densely if you switch to agriculture so that's what happens.
Agriculture -> cities which are only really possible because of the breeding for cooperation that took place in the earlier steps.
14/x
Agriculture -> cities which are only really possible because of the breeding for cooperation that took place in the earlier steps.
14/x
Now the selective pressure is different again; selecting for intelligence again, selecting for enough docility to avoid being enough of a danger to others that your genetic line ends via execution, enough cooperation that your city doesn't fall too cohesive raiders
15/x
15/x
That was another big step; cooperate enough with a wide enough group of men that you can produce wealth to produce weapons for armies that are equipped with increasingly sophisticated arms and armor.
16/x
16/x
Without going into the more recent steps this process seems to have bred in the weakness that has allowed what is basically social cancer to grow - cancer in that individual cells are prospering while killing the host.
17/x
17/x
Touching on one point from earlier though.
The nodes that are connected via an edge from the second continent are subject to the same broad forces as the Eurasian continent but the process starts many 1000s of years later.
Re-introduction has entirely predictable results.
18/x
The nodes that are connected via an edge from the second continent are subject to the same broad forces as the Eurasian continent but the process starts many 1000s of years later.
Re-introduction has entirely predictable results.
18/x
Counterfactual speculation - if the graph doesn't have more nodes away from the Eurasian node does the cancer spread?
You could make a case that it doesn't - that the evolutionary arms race forces are too strong, constantly pushing to a new local maximum.
19/x
You could make a case that it doesn't - that the evolutionary arms race forces are too strong, constantly pushing to a new local maximum.
19/x
So maybe the filter is:
Life, etc.
Need isolated continents
Can't have isolated continents that branch off only edge of the origin continent
Who knows what the probability of development like that is? Time to start studying exoplanet-plate tectonics
20/x
Life, etc.
Need isolated continents
Can't have isolated continents that branch off only edge of the origin continent
Who knows what the probability of development like that is? Time to start studying exoplanet-plate tectonics
20/x
