I'd be curious to hear what you guys have to say about the types and degree of impact (forgive the pun) that astronomical processes have had on terrestrial evolution.
Let's get two big ones which I know a little about out of the way first:
1.Impact:
Comets and meteors have pummeled the Earth and other surviving bodies in the solar system throughout its history. The evidence for this is overwhelming and some of it is quite literally under our feet. This would have been far more dramatic in the early stages of the formation of our solar system, when the number of bodies was greater and so then was the chance of impact. An equilibrium (of sorts) has been reached at the stage we now find ourselves, in which collisions are less common but still quite frequent in terms of the smaller meteorites that come down regularly.
There is overwhelming evidence that collisions have caused mass extinction events on the Earth. These would dramatically alter the potential course of evolution, resetting the parameters for survival and ending any hopes of it for a great many in one violent second.
Additionally, the very nature of this violent early stage may have prohibited early life from getting a foothold:
Paul Davies writes:
If Earth was pounded as fiercly as astronomers believe, and if surface organisms really were well-established by 3.8 billion years ago, then life must have burgeoned almost as soon as the effects of the last sterilizing impact were over.
Citing a study by Kevin Maher and David Stevenson from Caltech, the author goes on to discuss the possibility that life may have arisen in between cataclysmic periods only to get repeatedly wiped out:
Paul Davies writes:
"It is a curious thought that if life did form anew several times, then humans would not be descendants of the first living thing. Rather, we would be the products of the first life forms that just managed to survive the last big impact in this extended stop-go series."
Davies eventually gets around this whole conundrum by presenting evidence that the earliest life forms may have been subterranean and capable of withstanding enormous heat and conditions that we would class as extremely hostile. Their closest cousins may be mirrored in the hyperthermophiles that we find today.
2.Possible extraterrestrial origins of life:
The idea here is that life arose on some body other than the Earth and was deposited here via impact. This idea most often involves comets, and it has been shown that comets contain a great deal of organic material. It was confirmed earlier this year that the amino acid glycine was found in NASA's Stardust mission to Comet Wild 2 in 2004. Found: first amino acid on a comet | New Scientist
This is a fascinating area in its own right, but it really simply redefines the location of origin of the earliest life, and not the subsequent terrestrial evolution which I am discussing in the post.
The next two are where I definitely hope to hear what you guys think:
3.The Moon:
What effects has our moon had on evolution? There is an unmistakable connection between the moon and living things due to its gravitational pull (tidal patterns, menstrual cycles).
In what other ways has the moon influenced natural selection on Earth?
The reflected sunlight from the moon that comes and goes over the course of a month has undoubtedly played a role in various ecosystems, even if just by virtue of providing better light by which to hunt and/or gather.
The moon has undoubtedly played a large role in the cultures of human beings. I find it fascinating to think that it might actually have given us a head-start towards rationality in the sense that it provides a nearby reminder of order in the heavens, one that stands in stark contrast to the sun, and the two of which together provide an even greater insight to just what the hell is going on. What might it be like to evolve on a planet that had no moon? Or three moons? Would a three moon system have led to a more rapid understanding of physical laws, mathematics, astronomy?
4. Earth's tilted axis
What influence have the seasons on earth, thanks to its tilted axis, had on terrestrial evolution? Would it have been more advantageous to have had no tilt? Or, did this fact play a crucial role in evolution by driving adaptive features?
5. What else?
What other aspects of our astronomical history have impacted the course of evolution on Earth, and what might life be like if conditions had been otherwise?
(--- Science: human origins and evolution forum? That would be more accurate than big bang/cosmology, please ---)
Edited by Briterican, : Title change, note to admin re desired forum.
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