A few days ago biologists Alexei Sharov and Richard Gordon published a paper that sent shock waves throughout the academic community. In their paper titled Life Before Earth they propose that life originated before the formation of our planet. How did they come to this conclusion? Is it possible?
For further Hubski discussion on this topics check out the two posts below:
It's an interesting approach, too bad they decide to ignore data that doesn't match their theory. And even then it's perfectly possible that life evolved/got more complex faster in the beginning before the growth of complexity got to the current model, a kind of biological inflation, akin to the cosmological inflation.
That is a really interesting idea (re: biological inflation). The only reason I would be hesitant to accept that is that biological life is still an evolutionary process and the mechanisms required to build a complex cell would have operated at slower rates than those operating in multicellular organisms. But maybe lack of competition would have allowed for a quick proliferation? Maybe when life took a hold of the light elements on the planet that process happens very quickly? We don't know! It is a big mystery! I'm sure someone will test the biological inflation idea one day. I honestly think Earth was seeded with complex replicating chemistry during the Late Heavy Bombardment 4 billion years ago. I don't think that chemistry has pre-galactic origins, but it would explain why single-celled colonies appeared on Earth as soon as they possible could have (i.e. post-Hadean).
I really dislike this old idea, mainly because it was supported by Hoyle et al during his "steady state universe with transpermia" pseudo-creationist period. (But it can have older roots.) Besides being a cherry-pick, as you yourself notes at the end "evolution can produce trillions of species without ever selecting for high-intelligence". Confusing growth processes with any of the many ways to measure complexity is the other sleight of hand often used. Parasitic simplification is at least as common (with other half of species parasites), meaning there is no specific trend but a Gouldian diffusion to fill up a niche space. Mass extinctions tests that nicely, with diversity recovering to random levels, it can be a more or less complex system after a ME. [I don't have that ref handy.] Other minutiae is that biologists haven't checked with planetary scientists. Mojzics et al has shown that any realistic intensity of late bombardment can't sterilize a planet, cells procreate and disperse faster than impactors sterilize crust. (There is even a Goldilocks zone ~ 1 km down where crust busters are survivable somewhere else on a planet.) The earliest potential trace fossils are now the Isua BIFs @ 3.8 Ga bp, since small scale isotope analysis has shown that the later metamorphosed rocks were originally biologically deposited. So with Mojzics et al in mind, we don't really know when life appeared, because of later plate tectonics - few older rocks. A simple model [of my own] using the latest protein fold phylogenies gives a (linear, btw) extrapolation of the first gene ~ 4.10 Ga bp, which is reasonably after the first oceans appeared ~ 4.25 Ga bp [from the Jack Hill zirconium/diamond evidence.] Other concerns raised:
- Transpermia. Can't compete with local abiogenesis rates with the latest pathways such as Lane & Martin, or Russell et al. Even a martian tramway raining down flash frozen spores has too low transfer rate to make it the likeliest pathway if you take experimentally observed factors of survivability et cetera into account. - Fermi question. Too unconstrained due to potentially unobservable pathways (silent civilizations), making for false negatives. Need observed positives for making the full Drake equation a useful estimate. (The short DE for life at large works well for potentially observable inhabited, oxygenated worlds on the other hand, as we will only look for positives.)
I haven't read the word "panspermia" here yet. The idea that life here started on another planet and somehow landed on this earth through comets or alien garbage dumps. Like we are doing now on Mars. If Sharon's and Gordon's theory holds true this is the most viable option.
I end the article suggesting the possibility of panspermia (even indicating that I favour it):That is not to say that life could not have originated completely or partially from space. The idea that asteroids with complex organic compounds seeded our planet during the late-heavy bombardment 4 billion years ago is quite possible. But positing the chemical compounds necessary for life existed 9.7 billion years ago requires more evidence than a logarithmic scale with cherry picked data points.