Lately it seems to be popular to speculate that life may have originated on Mars through transfer of microbes through impact debris. Part of the mindset is that Mars cooled sooner than the Earth and may have been the source of life on Earth.

http://www.space.com/22577-earth-life-from-mars-theory.html

If this is true then this could explain the Cambrian "explosion", there are multicellular organisms tough enough to make the journey from Earth to Mars and by the time of the Ediacara life forms the Earth seems to have dominated by weird organisms with no modern counterparts.

A meteor holding desiccated specimens of some tough creature or creatures, already the result of billions of years of evolution but from the same microbes that seeded early Earth, could have been thrown to Earth from Mars by an impact , some tough creature already adapted to a competitive life style, toughened by the deteriorating conditions on Mars, transferred by impact debris, unable to compete was Earth's Ediacara biota wiped out and replaced by Martians!

What do you think?

 

 

 

I think the aquatic ape hypothesis people have a new toy.

I think the article by Armstrong and Sandberg, Eternity in six hours: Intergalactic spreading of intelligent life
and sharpening the Fermi paradox, makes panspermia planned by another civilization as likely as abiogenesis on either Earth or Mars. ATM there is no basis for estimating any of the possibilities AFAIK.

My thinking on this has to do with environmental change or stress leading to evolutionary changes. Mars would have been (in light of this idea) a hot bed of evolutionary change due to changing environmental conditions. Just before the Cambrian explosion life on Earth had been microbes for billions of years and the first multicellular life was not much more than flat sheets of cells filtering microbes from the water. Possibly sponges and jelly fish but not much more then almost suddenly animals that eat other animals appeared. Earth life, even now, has species that could survive the trip from Earth to Mars. a Mars with slowly degrading environmental conditions could have evolved many complex life forms with spore like stages, like vernal pool shrimp, or organisms that can survive desiccation like water bears. In fact logically Mars should have evolved more life forms capable of waiting out long periods of bad environmental conditions due to deteriorating conditions like droughts.

 

 

Such life forms would be "pre-evolved" for transport to Earth via impacts...