
What a Newfound Kingdom Means for the Tree of Life (2018) - curtis
https://www.scientificamerican.com/article/what-a-newfound-kingdom-means-for-the-tree-of-life/
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bsaul
Wonder if biology is going to experience the same transition from inheritance
to composition that computer science went through those last two decades, and
stop building trees of classes, but rather favor describing species by a
composition of elementary attributes.

~~~
goatlover
No, because the tree of life is based on common descent for the various
populations going back to a single ancestor in the very distant past.

~~~
chousuke
Makes me wonder, was it actually a literal "single ancestor" at any point, or
are we be the result of several completely unrelated populations doing
horizontal gene transfers (or whatever it would've been before actual genes
were a thing)?

What little I know of what we know, it doesn't seem completely implausible to
me for self-replicating molecules to have appeared multiple times on the young
Earth. Is it possible for these hypothetical multiple starts to have been be
chemically compatible?

~~~
PaulHoule
There was a huge horizontal gene transfer event when us Eukaryotes were born
from a train crash between the Bacteria and the Eubacteria. Thus you can't
trace out a single "tree" of life all the way to the root.

~~~
chousuke
I'm vaguely aware of that, but I was thinking about life even earlier. That
is, instead of having a single universal common ancestor to all life that
currently exists, would it have been possible to have a set of separate
strands of life that arose from abiogenesis (or however it started) and later
merged?

I like the thought, though I'm aware that that alone doesn't make it more
likely to be true. I'm just wondering if we know something that rules out the
possibility.

~~~
tempguy9999
> to have a set of separate strands of life that arose from abiogenesis (or
> however it started) and later merged?

Not impossible but likely ever impossible to prove.

I have read a theory that in the earliest days before impermeable cell walls
formed, all dna (or whatever it was then) was being madly swapped around
because horizontal transfer couldn't be stopped. No lineage then, but an
amorphous glob of all life. When life got more sophisticated it then
differentiated, because it could block horizontal transfer. But again, who
knows.

~~~
TeMPOraL
'Madly swapping DNA around' happens to this day at the bacterial/archaeal
level.

The argument against multiple "strands" of life is simple: if abiogenesis of a
single replicator is extremely improbable, abiogenesis of multiple such
replicators is much less likely still. Plus, almost by definition, the first
successful replicator will start replicating and eating all it can around
itself, strongly altering environmental conditions and closing the doors for
anything that could spontaneously arise after it.

~~~
tempguy9999
> if abiogenesis of a single replicator is extremely improbable

If [0]

> the first successful replicator will start replicating and eating all it can
> around itself

Assuming such life looked much like it does now, yes. It may, it may not.

I'm not disagreeing with you, these are valid points but we can't know and I
am uneasy about speculating in such a case.

[0]
[https://en.wikipedia.org/wiki/Laconic_phrase](https://en.wikipedia.org/wiki/Laconic_phrase)

After invading southern Greece and receiving the submission of other key city-
states, he [Philip II of Macedon] turned his attention to Sparta and asked
menacingly whether he should come as friend or foe. The reply was "Neither."

Losing patience, he sent the message:

"You are advised to submit without further delay, for if I bring my army into
your land, I will destroy your farms, slay your people, and raze your city"

The Spartan ephors again replied with a single word:

"If"

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PaulHoule
Biologists have long known that most microbes are "dark matter" in the sense
that we don't know how to culture them independently.

There are all sorts of strange things such as huge rod bacteria that have lots
of little rod bacteria living on their surface.

Many unknown organisms make themselves visible through their DNA, but without
the ability to culture them independently we can't tell which are which.

~~~
ianai
They called it part of the known unknowns in the article.

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akkartik
The 'scoreboard' at
[https://en.wikipedia.org/wiki/Eukaryote#Classification](https://en.wikipedia.org/wiki/Eukaryote#Classification)
makes for fascinating reading.

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carapace
I have to mention this (linked from the OP)
[https://blogs.scientificamerican.com/artful-
amoeba/surprise-...](https://blogs.scientificamerican.com/artful-
amoeba/surprise-discovered-inside-shaggy-shimmying-protists-video/)

Not to spoil it but there's a _rotating_ organelle(?)! (Among other things.)

And these rocket-propelled harpoons:

[https://blogs.scientificamerican.com/artful-amoeba/marine-
mi...](https://blogs.scientificamerican.com/artful-amoeba/marine-microbes-
exchange-fire-with-elaborate-subcellular-weapons-video/)

Just wow.

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mighty_bander
Archaea are interesting and often overlooked because they aren't numerous
relative to bacteria. The domain Archaea always struck me as more of a "junk
drawer" than a genuine grouping.

~~~
madhadron
> Archaea always struck me as more of a "junk drawer" than a genuine grouping.

Why do you say that? They emerged from the large scale structure of 16S rRNA
trees, which is what defined them as separate from bacteria.

~~~
stochastic_monk
You’re correct, the above poster is more enthusiastic than accurate. I knew
Carl Woese, who discovered Archaea through this analysis, during my time at
UIUC.

