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Re: Sinosauropteryx filament melanosomes challenged
I agree with everything you say, but I think the concept of "higher"
life has its uses when placed in a larger context. The universe as a
whole seems to self complexify; that is to say that the universe
started out as simple particles, then matter, accretion disks, stars,
planets, primitive self replicating polymers, DNA based life etc.
Endothermic life has a higher potential to evolve larger more complex
brains, which in turn can lead to technology, which in turn could
lead to artificial life, until for all we know, something like a
matryoshka brain (or Dyson sphere) is the "end" result; the entire
process could often culminate (all over the universe) into something
that is as far "above" us in energy usage and complexity than we are
above bacteria. So while evolution doesn't have a "goal" and it's not
a ladder to be climbed, it is a process that tends to produce
increasingly complex systems that may increase in both the rate and
quantity of total energy consumed/used.
You have counted the hits and ignored the misses.
The _diversity_ of complexity is increasing, which is not surprising,
because both life and the universe started around the minimum possible
complexity. But is the mode moving anywhere?
The vast majority of living beings are still bacteria and archaea, and
the most complex among these are not the most common ones. The vast
majority of the universe is still vacuum.
In Gould's words, you are looking at the tip of the right tail of the
truncated Gauss curve, and you ignore the entire rest of the curve.
So in this context, I would definitely say that archosaurs and
mammals are higher forms of life than reptiles, but not because they
are "superior" but because they tend to be more complex, more
intelligent, use more energy and have the potential to produce
Looks like an arbitrary selection of criteria to me.
Besides, how do you measure complexity? Eyeballing large differences in
complexity is easy, but measuring the details is impossible -- or, at
least, it requires a very detailed definition of "complexity" that has
not yet been found. Biologists have stopped looking for one.
Furthermore, what is it about any of these traits that warrants a
"higher status" than, say, a bacterium that can swap in arsenic for
phosphorous in its DNA?
There's no evidence that the arsenate is part of the nucleic acids and
proteins (and mysteriously stabilized against hydrolysis), as opposed to
just lying on top of them. Phosphate is said to be sticky like that,
which doesn't surprise me for electrostatic reasons. The news value lies
in the fact that that gamma-proteobacterium can grow at all in the
presence of that much arsenate, which requires keeping the arsenate out
of its ATP synthase and its phosphorylases.
BTW, phosphorus is not an adjective.
Actually, there are ecosystems on the sea floor that exist entirely
independently of the Sun. Heat (geothermal) and nutrients (such as
sulfur compounds and methane) are provided by hydrothermal vents,
and chemosynthetic (rather than photosynthetic) microbes provide the
base of the food chain. These ecosystems include not just
chemosynthetic microbes, but a diverse array of invertebrates (clams,
shrimp, and various types of worms). If the Sun died out, these
organisms would presumably go on living.
The chemosynthesis in question generates ATP (much of which is used to
turn carbon dioxide into sugar) using the energy that comes from turning
sulfide into sulfate. That requires hydrogen sulfide and...
...oxygen. Oxygen that comes from higher up in the water column, from
photosynthesis. Hydrothermal ecosystems are by no means independent of
the sun. Only their _carbon_ doesn't come from photosynthesis; their
The animals in hydrothermal ecosystems are ordinary heterotrophic
animals that eat organic matter and breathe oxygen.
There are indeed anaerobic ecosystems that _are_ independent of the sun.
But those are bacterial and/or archaeal ecosystems deep in the solid
rock. Their energy ultimately comes from radioactivity.