Evolution: life below ground (Evolution)

by David Turell , Monday, December 10, 2018, 19:11 (2173 days ago) @ David Turell

New borings to five kilometers find enormous amounts of life:

https://phys.org/news/2018-12-life-deep-earth-totals-billion.html

"Barely living "zombie" bacteria and other forms of life constitute an immense amount of carbon deep within Earth's subsurface—245 to 385 times greater than the carbon mass of all humans on the surface, according to scientists nearing the end of a 10-year international collaboration to reveal Earth's innermost secrets.

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"With insights from now hundreds of sites under the continents and seas, they have approximated the size of the deep biosphere—2 to 2.3 billion cubic km (almost twice the volume of all oceans) - as well as the carbon mass of deep life: 15 to 23 billion tonnes (an average of at least 7.5 tonnes of carbon per cu km subsurface).

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"Among many key discoveries and insights:
The deep biosphere constitutes a world that can be viewed as a sort of "subterranean Galapagos" and includes members of all three domains of life: bacteria and archaea (microbes with no membrane-bound nucleus), and eukarya (microbes or multicellular organisms with cells that contain a nucleus as well as membrane-bound organelles)

"Two types of microbes—bacteria and archaea—dominate Deep Earth. Among them are millions of distinct types, most yet to be discovered or characterized. This so-called microbial "dark matter" dramatically expands our perspective on the tree of life. Deep Life scientists say about 70% of Earth's bacteria and archaea live in the subsurface

"Deep microbes are often very different from their surface cousins, with life cycles on near-geologic timescales, dining in some cases on nothing more than energy from rocks
The genetic diversity of life below the surface is comparable to or exceeds that above the surface

"While subsurface microbial communities differ greatly between environments, certain genera and higher taxonomic groups are ubiquitous—they appear planet-wide

"Microbial community richness relates to the age of marine sediments where cells are found—suggesting that in older sediments, food energy has declined over time, reducing the microbial community

"The absolute limits of life on Earth in terms of temperature, pressure, and energy availability have yet to be found. The records continually get broken.

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"Led by Cara Magnabosco of the Flatiron Institute Center for Computational Biology, New York, and an international team of researchers, subsurface scientists factored in a suite of considerations, including global heat flow, surface temperature, depth and lithology—the physical characteristics of rocks in each location—to estimate that the continental subsurface hosts 2 to 6 × 10^29 cells.

"Combined with estimates of subsurface life under the oceans, total global Deep Earth biomass is approximately 15 to 23 petagrams (15 to 23 billion tonnes) of carbon.

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"Molecular studies raise the likelihood that microbial dark matter is much more diverse than what we currently know it to be, and the deepest branching lineages challenge the three-domain concept introduced by Carl Woese in 1977. Perhaps we are approaching a nexus where the earliest possible branching patterns might be accessible through deep life investigation.

"Ten years ago, we knew far less about the physiologies of the bacteria and microbes that dominate the subsurface biosphere," says Karen Lloyd, University of Tennessee at Knoxville, USA. "Today, we know that, in many places, they invest most of their energy to simply maintaining their existence and little into growth, which is a fascinating way to live.

"Today too, we know that subsurface life is common. Ten years ago, we had sampled only a few sites—the kinds of places we'd expect to find life. Now, thanks to ultra-deep sampling, we know we can find them pretty much everywhere, albeit the sampling has obviously reached only an infinitesimally tiny part of the deep biosphere."

Comment: First it is obvious the Earth allows life everywhere and it is amazingly life-friendly. The next question is how did those organisms get down there? Did they first evolve on the surface and then slowly go deeper? If they suddenly went that deep they could not have evolved to the forms they are now, which are markedly different from surface bacteria. Were they designed to be there? That could be God at work running the evolutionary process.