The Impossibility of Intelligent Life

[DaveC426913]

...water is a rather special chemical...

• Is there a chemical analogue for water? Is there anything that could substitute it biologically? And could any such analogue exist under different planetary conditions as a liquid?

What do you have against water? It's one of the most abundant 3-atom molecules in the universe.

Looking for substitutes is kind of like saying "Sure, there's acres of grass for horses, but what is there for zebras?"

 

[zoobyshoe]

Right. I see where Evo is coming from. It's similar to wolves and dogs; both canines, but distinct species (that can interbreed) which challenges a rigid notion of "species" in the first place, since interbreeding is part of the definition of species.

Order, then, has been restored in the universe, and there's hope for world peace.

 

[Evo]

Right. I see where Evo is coming from. It's similar to wolves and dogs; both canines, but distinct species (that can interbreed) which challenges a rigid notion of "species" in the first place, since interbreeding is part of the definition of species.

Yes!

 

[Drakkith]

Are you guys forgetting Neanderthals and Denisovans?

http://www.nature.com/news/hominin-dna-baffles-experts-1.14294

Yes. I did indeed forget about our now-extinct pals.

 

[Pythagorean]

Here's an interesting article that just came out a couple days ago where they have put a particular brain growth gene (HARE5) from humans in mice and they grew bigger brains, whereas the chimpanzee version of HARE5 did so to a lesser degree:

http://www.cell.com/current-biology/abstract/S0960-9822(15)00073-1

I can't access it with my creds, which is strange, because I usually can with cell, but I want to know what happened to the mice . Though, I think I found the thesis by the same grad student from which the paper was probably generated. There's probably going to be a lot of background on human brain evolution in the introduction:

http://gradworks.umi.com/36/67/3667365.html

Another good resource is Jon Kaas, Evolutionary Neuroscience:
http://store.elsevier.com/Evolutionary-Neuroscience/isbn-9780123751683/

Anyway, I think the answer to the OP is basically "the right set of mutations at the right time in their evolutionary history", HARE5 being an example.

 

[collinsmark]

Sorry if this disrupts the flow of conversation, but this thread deserves at least a reference to the Drake equation.

The Drake equation is not derived, so to speak. It is a completely contrived equation. But it functions quite well in breaking down the essence of so many questions put forth in this thread into their constituent parts.

The Drake equation:
$$N = R_* f_p n_e f_{\ell} f_i f_c L,$$
where

• $N =$ The number of civilizations in The Milky Way Galaxy whose electromagnetic emissions are detectable.
• $R_* =$ The rate of formation of stars suitable for the development of intelligent life.
• $f_p =$ The fraction of those stars with planetary systems. This particular variable is of interest as of late. Only a couple of decades ago it was unknown if our system was unique in terms of having planets. But now with more recent discoveries (the Kepler satellite observations, most notably), we now know that planets around stars are perhaps the norm, rather than the exception.
• $n_e =$ The number of planets, per star system, with an environment suitable for life. Note that this is not necessarily a fraction; the variable could, in principle, be greater than 1. It relates to the average number of planets, per suitable star system that has planets to begin with, that are in the "Goldilocks zone," among other things such as having water and whatnot.
• $f_{\ell} =$ The fraction of suitable planets on which life actually appears. This means any type of life: not limited to intelligent life.
• $f_i =$ The fraction of life bearing planets on which intelligent life emerges. Of those planets that have life, this is the fraction of how many bear intelligent life.
• $f_c =$ The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
• $L =$ The length of time such civilizations release detectable signals into space.