Miscellaneous: more on LUCA study (General)

by David Turell , Saturday, December 07, 2024, 18:54 (14 days ago) @ dhw

From Hossenfelder:

https://www.patreon.com/posts/new-study-of-117456284/early-access?token=eyJhbGciOiJIUzI...

"If you trace back your genetic family line a few billion years, it doesn’t only join with mine, it joins with those of all known animals, and plants, and bacteria, to one organism: LUCA, the Last Universal Common Ancestor. Scientists believe that every living thing on Earth descends from LUCA, it’s just taken us about four billion years to learn speaking English.

"But a recent study delivered quite a surprise. It’s found that LUCA was much more complex than previously thought, and that raises a lot of questions about the origin of life.

"LUCA is a hypothesis, but a well motivated one. It’s based on the observation that all living beings on earth are built up in similar ways. They all have similar molecular and cellular features, such as the genetic code, ribosomes, and metabolic pathways like the way we generate energy from sugar. And to the extent that we can test this with fossils, it’s also the case well back in time.

"Scientists think that LUCA was not the origin of life itself. There were likely simpler self-reproducing structures before that, though it somewhat depends on what you mean by “life”. If life means arguing about the Oxford Comma, I don’t think LUCA was quite there yet. But just exactly what sort of organism LUCA was, no one really knew. This is where the new study comes in.

"These researchers did a sophisticated genomic analysis of pretty much everything they could get their hands on to identify the genes which all known organisms have in common and which therefore likely originated in LUCA. They found a whopping 2,657 of them, much more than any previous study.

"And we mostly know what these genes are good for, because we know what proteins they synthesize. The genes seem to indicate that LUCA was good at using hydrogen gas as an energy source. This is very interesting because it tells us something about the environment in which LUCA must have lived. (my bold)

***

"That part had it that when LUCA lived, about 4 point 2 billion years ago, organism were incredibly basic.

"But this is not what the new study found. Even though this study might have missed some genes, it gives us a minimal set of what LUCA must have contained.

"They estimate Luca’s genome size to be about 2 point 75 million base pairs of DNA. Just for comparison, human DNA has a little over 3 billion base pairs and onions about 13 billion.

***

"They write in the paper “The result is a picture of a cellular organism that was prokaryote grade rather than progenotic and that probably existed as a component of an ecosystem,”

"This basically means it’s more complex than they thought. Prokaryotes are organisms that still live today, for example many types of bacteria like E coli. They are typically 1 to 10 micrometres in size and have a cell wall but no nucleus that holds the DNA. Instead, the DNA floats freely on the inside.

"The reason this is relevant is that we know roughly when LUCA existed and there wasn’t a lot of time for it to grow to that complexity because just half a billion years earlier, Earth was quite literally a hot mess. So this study means that either life can form much easier and faster than we thought, or it was seeded by some sample from outer space. (my bold)

Comment: note my bolds. My view is that life appeared as engineered by God, just like the Cambrian animals did later on. It only took half a billion years to appear once the earliest Earth had formed.