I was listening to a talk by Stephen Webb where he briefly ran through what he says is the current understanding of how life originated on our planet. I realize he is a popularizer, not a scientist, but he says that life emerged from pre-life chemical reactions that gave rise to life through abiogenesis. And that things got really off and running when those early “life” forms stumbled onto a way to reproduce themselves (RNA?).
This got me to wondering, are there places on earth where those types of chemical reactions are still washing together into what could be called life (albeit, non-reproducing life)?
I realize that even if so, those types of life would probably get gobbled up too quickly to have a chance to evolve but just wondering if those same processes are still at work.
AFAIK, no.
The chemical reactions that were the precursor to life required a reducing atmosphere. Those reactions can’t occur in an atmosphere with free Oxygen in it. Also, the current atmosphere doesn’t have enough methane to make the reactions very likely.
I don’t know that I would be as sure. Oceanic vents and places deep in the crust may have a similar environment to the early Earth.
That said, those nooks are probably taken up by existing life, leaving nowhere for proto-life chemical reactions to occur.
Interesting thing I came across recently is that part of the reason that photosynthesis is fairly inefficient is because it evolved in a oxygen free atmosphere, then essentially kludged together a system to deal with the oxygen when it started building up.
Some progress was announced recently when finding out how proteins worked with metals.
Addressing one of the most profoundly unanswered questions in biology, a Rutgers-led team has discovered the structures of proteins that may be responsible for the origins of life in the primordial soup of ancient Earth.
The study appears in the journal Science Advances.
The researchers explored how primitive life may have originated on our planet from simple, non-living materials. They asked what properties define life as we know it and concluded that anything alive would have needed to collect and use energy, from sources such as the Sun or hydrothermal vents.
In molecular terms, this would mean that the ability to shuffle electrons was paramount to life. Since the best elements for electron transfer are metals (think standard electrical wires) and most biological activities are carried out by proteins, the researchers decided to explore the combination of the two — that is, proteins that bind metals.
“We saw that the metal-binding cores of existing proteins are indeed similar even though the proteins themselves may not be,” said the study’s lead author Yana Bromberg, a professor in the Department of Biochemistry and Microbiology in the School of Environmental and Biological Sciences at Rutgers University-New Brunswick. “We also saw that these metal-binding cores are often made up of repeated substructures, kind of like LEGO blocks. Curiously, these blocks were also found in other regions of the proteins, not just metal-binding cores, and in many other proteins that were not considered in our study. Our observation suggests that rearrangements of these little building blocks may have had a single or a small number of common ancestors and given rise to the whole range of proteins and their functions that are currently available – that is, to life as we know it.”
The same issues undoubtedly apply to all earlier eras as well. Once life as we know it got established on earth, it had the ability to outcompete newer and different forms just emerging. Life of several kinds could have appeared multiple times over the eons and been completely wiped out without leaving any trace.
Or not. Even in theory, no one has given a way to know for sure.
Interesting. I often hear, in talks like these, that life basically emerged on earth as soon as the conditions were right. So if all life were suddenly extinguished, from say radiation, that would mean it wouldn’t have much of a fighting chance to re-establish itself.
There are IIRC about 7 trillion cells in the human body. Chemical compounds are several orders of magnitude smaller than that. So imagine the volume of lakes and ponds and tidal pools along the major coastlines and subject to lightning strikes, cosmic rays, and assorted other reaction drivers in the primordial earth - the odds of chemical compounds forming in interesting ways would be pretty likely given that immense volume of working material. I believe it was the Miller experiments that demonstrated how easily and quickly some more complex organic molecules could form given that sort of primordial soup.
Once compounds could form catalyst shapes that produced reproduction of those compounds, then the odds are that growing complexity became more likely.
That is difficult to say exactly because there are a number of cofounding factors, but there about 1.1 x 1015 metric tons of oxygen in the atmosphere, and estimated annual production of oxygen is ~17.75 GT (16.01 GT from land sources, 1.74 GT outgassing from the ocean). So if you assume that removing the oxygen production results in a linear deficit of atmospheric oxygen, that gives about 62 kyr before oxygen is depleted. (We are actually in a progressive decline in atmospheric oxygen and have been so for about the last 800 kyr, but only by a fraction of a percent in that time, the trend of which has been dwarfed by the increase in anthropogenic atmospheric carbon dioxide pushing that percentage down.)
In reality, the oceans produce far more oxygen than they outgas, and stay in relative balance with the atmosphere at the surface layer, so you’d expect an increase in outgassing—and thus a reduction in the rate of atmospheric oxygen depletion—until they were in balance. As atmospheric oxygen levels drop, the consumption of oxygen by respirating organisms (which would presumably die off en masse) would reduce consumption, as would non-living forms of oxygen consumption such as fires. About 2% of total oxygen production is from non-living sources (mostly lightning and charged particle interactions in the upper atmosphere) so there would be some residual level of free oxygen in the fractional percentage range. Since there aren’t processes ejecting masses of carbon or sulfur into the air the Earth’s atmosphere could not turn into a runaway greenhouse to the extent that Venus is but it could certainly become too warm and depleted of oxygen to support any complex life as we know it.