Naked Science Forum
Life Sciences => Cells, Microbes & Viruses => Topic started by: syhprum on 30/07/2018 08:20:29
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Whenever possible lifeforms on other planets are discussed it is suggested they are primitive yet complex life forms on the Earth evolved in less than half a billion years.
Why this attitude is the Earth the only planet where evolution is possible ?
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The conditions under which evolution (that we would recognise as such) is possible, are limited and transient. Eventually all the surface water will disappear and this planet will look pretty much like Mars. Thus the balance between plants and animals, and competition for resources, will alter beyond recognition and evolution will take a very different course.
"Primitive" as judged instantaneously generally refers to having an alien intellect or culture. At present we have only an instantaneous view of other planets so everything looks primitive, but on closer examination of the archaeology of another planet we may indeed be able to trace an evolution of that culture.
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Whenever possible lifeforms on other planets are discussed it is suggested they are primitive
I watched a documentary over the weekend about the search for extra-terrestrial life, and they pointed out that there are stars in our galaxy that are much older than the Sun, and life there could be far more advanced than life on Earth.
Of course, if you go to really old stars, they have to be red dwarf stars, and the "goldilocks zone" is so close that any planets are likely to be tidally locked. That means there is a very narrow habitable zone, or incredibly strong winds (or both). So ecosystems there would be very different than what we see on Earth.
As usual, we focus on life-as-we-know-it (ie based on water+carbon).
Because we don't know what to expect from life-but-not-as-we-know-it.
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I'm not entirely comfortable with the implications of your statements and questions. Thus the title "Why is Earth the only planet on which evolution has worked?" is a strawman. We do not know if evolution has worked on other planets or not.For example, Mars may have extensive subterranean lifeforms that have been evolving away quite happily for as long, or longer, as life on Earth.
Perhaps you meant "Why has evolution not produced complex lifeforms on other planets in the solar system?" In brief, the conditions have not been favourable to the development of complex lifeforms on the other planets. Since we only have Earth life as an example it is risky to speculate too deeply about what constrains or favours the development of complexity.
As a side note, it is probably a matter of translation, but the phrase "evolution has worked" implies that evolution has a purpose. Evolution is primarily a consequence, not a cause. It has not been demonstrated to have a purpose.
Whenever possible lifeforms on other planets are discussed it is suggested they are primitive yet complex life forms on the Earth evolved in less than half a billion years.
We must be reading different material. There are plenty of discussions that envisage complexity to be commonplace. Perhaps you have been (over)exposed to the work of Ward and Brownlee who, in Rare Earth, developed a well structured and soundly supported argument that life in the universe was probably commonplace, but that intelligent life was extremely rare. There is no solid consensus among exobiologists (that I am aware of) that supports this view, though it is well regarded.
Why this attitude is the Earth the only planet where evolution is possible ?
This is not an attitude I have seen expressed anywhere - that includes popular science articles, popular science books, textbooks, monographs, technical literature in peer reviewed journals. Could you give two or three examples of where you have run across such attitudes?
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I think it's the consensus that most habitable planets would have primitive life compared to us rather than all of them. This is because extremophilic microbes have a significantly larger range of environmental tolerances than complex multicellular organisms do. There are quite a few microbes that thrive in oxygen-free conditions, but molecular oxygen (or some similarly potent substance) is required for the energy-intensive functioning of almost all animals. Molecular oxygen is rare, so you could conceivably have microbes in such places as the Martian subsurface or the clouds of Venus but animal life would be unlikely.
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"Why is the Earth the only planet where evolution has worked"
There is no scientific evidence to back up that claim. Every planet in existence, has not been studied, and I do not even think it would be greater than 2% Then you have to factor in life based on what, and evolution thereafter. There could be methane based forms of life we have not even thought to look for.
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Evolution.
If I take an empty bucket out 2 d sea shore or beach n fill it up with sea water...n if on very close microscopic scanning I do not find any fish inside of it...can I say dat there r no fish in d whole sea, or no fish exist in all d oceans...
I Guess Not.
Primitive VS Complex.
We know & r aware about various relationships, affairs, heartbrks & 1 nite stands dat Gaia has gone thru...hence her children seem complex.
But dat dosnt mean all d others r innocent maidens or virgins.
Dey mite have had d times of their lives already, n just maybe their children live amongst us, as Geniuses.
Bottom line - only thoughts r primitive, d simplest of lifeforms r complex.