The first complex cells had genes from a complex mix of species
- Thread starter JournalBot
- Start date
To the author: you mention:
But I don't think you actually name this person anywhere, though it's clear from context that it's a specific person you have in mind. I'm wondering if some text went astray in the shuffling of the copy-editing process?
Upvote
11
(11
/
0)
More so than you expect. In Norse mythology, the Asgardians were a mix of the Aesir and Vanir tribes, many of whom had mixed blood with giants...
Upvote
2
(2
/
0)
Lynn Margulis. Although some of her ideas have origins in Russian biologists of a much earlier era, when the evidence had not yet grown to critical mass (Symbiogenesis)
Upvote
10
(10
/
0)
Aha. I'm no biologist (biology Hard!), but even I've heard that name. It may be she's so famous that the author thought it would be insulting the readership to spell out the name, which would be fair enough (ie, I'm more ignorant about the subject than anyone can easily comprehend).
Upvote
3
(3
/
0)
Upvote
5
(5
/
0)
Great article. It's amazing to me how much we've learned about that stage of evolution just even in the past couple decades. For example, I can remember having arguments with other grad students about endosymbiosis back in the early 1990s, when it was just emerging from being a fringe idea. The purist in me wishes everything was "cleaner" origin-wise, but there's definitely a certain satisfaction in being able the ancestral line all the way back to a gloriously chaotic melting pot.
Upvote
7
(7
/
0)
It is not conclusively established that the first life forms were bacteria or archaea, or even bacteria-like or archaea-like. Charles Kurland has argued that it's the other way around: the first life forms were more like eukaryotes (minus mitochondria and chloroplasts), and that bacteria are the evolutionary path towards rapid growth, simplification, and harsh environments, while archaea are the path towards extremely harsh environments. We musn't forget that life originated in an anoxic environment, radically different from today's environment. Atmospheric oxygen was poison to most lifeforms!
Upvote
1
(1
/
0)
Horizontal Transposon Transfer (HTT) is quite common in aquatic species, and most believe that they are often involved with gene transfers too, similar to viruses - it wouldn’t be a surprise if they took pieces of protein coding genetic material with them. For a gene transfer event to succeed, the transferred gene should be present in the germ cell, and should be propagated. Not that easy for multicellular complex organisms - especially terrestrial organisms, as air is really not that conducive as water for transfer of biological material. However, not an issue for early stage single cell lifeforms, if they were in water.
The question I wonder is, during early stages of life, were such transposable elements present ? As genetic elements, they are quite similar to viruses, and they might (more or less should) share common origins.
The question I wonder is, during early stages of life, were such transposable elements present ? As genetic elements, they are quite similar to viruses, and they might (more or less should) share common origins.
Upvote
1
(1
/
0)
Hoo boy. I didn't watch the lecture, but I did skim a few of his papers. This isn't my field but I've seen this kind of thing in areas closer to my expertise. What Kurland says shares a lot in common with... let's call them very old guard scientists to be polite, who reject pretty much all of modern molecular biology and phylogenomics to cling to outdated fringe theories. (e.g. bats are really primates - a fringe idea that was maybe worth a bit of consideration many decades ago, but complete nonsense once examined with modern genetics.)
The citation networks only reinforce my impression. He clearly isn't taken seriously enough to be considered worth citing by the mainstream, and is cited by the definitely-crazy-fringes that never had the benefit of a connection with established science.
Upvote
11
(12
/
-1)
Based only on 60+ years reading about the evolution of life, and in looking at the timelines and what likely happened from the fossil records, one needs to remember that complex life on Earth has only been around for less than a billion years. Closer to 600 million, actually.
So for nearly 4 BILLION years, the evidence is that life was not very complicated, and probably did live in microbial mats, probably in the oceans, probably near thermal vents where "food" came to you or at least provided the energy for life to begin and evolve.
Then, around 550 million years ago, life hit a tipping point where conditions and evolution converged to create new forms and families. Environmentally and biologically, life diversified into the forms we know today.
Howsoever long ago the microbial mats first appeared is still quite speculative, but it was likely billions of years back. And they'd have no predators, with what would be a very stable environment (earthquakes and the occasional meteor strike not withstanding) in which to exist.
So, current science suggests that microbial mats were a thing and that they'd been around longer than complex life has by anywhere between four to six times longer than the amount of time more complex life has even existed.
So all evidence to date so far already supports the if in that sentence. And the evidence could reveal that microbial mats could have been around longer than science so far has confirmed.
Upvote
0
(1
/
-1)
before 600 million years ago there is no much evidence for multicellular life. But the cells themself can still be quite complex. And if we look at the animal and plant kingdoms the cells are quite similar. So for a few hundred million years they didn't change much structurally. Only iterative refinements here and there.
We just happen to focus more on the larger living things, since that's the only thing we can see in the fossil record. But for about 2-3 billion years before the cambrian explosion , there was a lot of time (with short generations ) for cellular evolution. And , not impossible (here i am going on fringe), those were actually brought on earth by some comet pieces from much older planet. That can easily extend the available evolution time by a few more billion years.
Last edited:
Upvote
0
(0
/
0)
Ai yi yi. Apparently you are defining complex as "multicellular with functional differentiation" or something. At the very least, you have not shared your definition.
Eukaryotes have been around much longer than that. Here is just one article: 1.63-billion-year-old multicellular eukaryotes from the Chuanlinggou Formation in North China
Multicellular prokaryotes have been around much longer than that if you don't require differentiation. What do you think those "microbial mats" are? Bacteria and algae have been associating in one dimensional and two-dimensional units for at least 3 billion years. And there is no reason to believe that the prokaryotes that made up stromatolytes were all the same species.
Stromatolites: The Earth's Oldest Fossils
And also, some single-celled organisms are incredibly complex. Consider dinoflagellates, some of which can switch between different phases of their range of lifestyles. Spherical organic-walled microfossils known as acritarchs, some of which may be dinoflagellate hystrichospheres, first appear in rocks about 1.8billion years old...
Upvote
4
(4
/
0)
Not so sure why you seem confident that there were no predators around. It's not all happy good times between species at the microbial level. There is plenty of competition with species trying to out compete or outright kill each other.
Not sure if you would consider a virus a predator or not, but there is plenty of evidence that they have been around a long time hijacking cellular machinery for their own ends while killing their hosts.
Upvote
2
(2
/
0)
When we are talking about predators, we conveniently exclude vegetarians. I guess at the very beginning there were eaters of "primary producers" (a.k.a vegetarians) and detritivores
Upvote
1
(1
/
0)
multicellular eukaryotes are like builds of smart home appliances . The underlying parts are quite complex, and the integration might be quite thin...
Upvote
0
(0
/
0)
When you get down to the single cell level, what is a predator? Is an ameboma a predator when it eats a single cell algae? What if it eats another ameboma?
Upvote
1
(1
/
0)
and even our own cells can act like an amoeba (phagocytes are famous for that )
Upvote
1
(1
/
0)
Agreed, it's not mainstream, and I'm not endorsing his view, but his talk is still thought provoking, because we don't actually have evidence that the ancestors of eukaryotes were bacteria, archaea, or anything like bacteria or archaea. Yes, eukaryotes probably acquired mitochondria (and chloroplasts) through endosymbiosis with bacteria, or organisms that were like bacteria; no argument there. But that doesn't mean that bacteria are more ancient than the pre-mitochondrial eukaryotes just because bacteria and archaea are simpler. There is a logical fallacy out there: the earliest life forms must have been simple (yes); bacteria and archaea are simpler than eukaryotes (yes); therefore the earliest life forms must have been more like bacteria and archaea than like eukarotes (no).
Upvote
-1
(0
/
-1)
The fuck we don't. Did you not read the article? I am also guessing you don't know anything about population genetics.
Upvote
1
(1
/
0)
But we do have that evidence in the phylogenomics of Lokiarchaea! The discovery is relatively new, sure, and sure to be revised. This latest paper is just one of many filling in the details, again with truly massive amounts of data that identifies sets and likely sequences of horizontal gene transfers that occurred in early eukaryote evolution, before, during, and after mitochondrial endosymbiosis.
That's my point, that genetics is evidence, truly massive and robust evidence in many cases, and skepticism of its value is approaching a half century out of date. Sure you might not be impressed by the sequences of the first mitochondrial genes hand-aligned to something that was manually recognized to be a candidate ortholog in Proteobacteria. Or the first clades assembled based on one little highly conserved gene (18S sequences). That was the early-mid 80s.
Now, however, the amount of genomic and metagenomic data we have is truly astounding, orders of orders of magnitude more and higher quality. There are similar orders of orders of magnitude imrpovement in the statistical methods and raw computation available to handle that data. Bring it to evolutionary biology, and you have phylogenomics which is quite exquisitely powerful.
Upvote
1
(1
/
0)
All a matter of perspective - plant biologists will describe any herbivore as a predator! There's some room for finer definitions, whether a particular herbivore is likely to eat the entirety of a plant (by itself or as part of a swarm) or just nibble a bit on parts that will regrow which might be called micropredation. Either way, when talking about early life terms like "heterotroph" vs "autotroph", further divided into categories like "organoheterotroph" or "photoautroph", do most of the heavy lifting.
Upvote
1
(1
/
0)