3 ms·

There are so many examples of convergent evolution [0] here on Earth that it seems reasonable to speculate that many of the most useful compounds for life would

There are so many examples of convergent evolution [0] here on Earth that it seems reasonable to speculate that many of the most useful compounds for life would evolve similarly many times over a large number of trials/planets. Since we don't have access to such data, some metrics that seem useful for speculation about a property are: - How often it has evolved independently on Earth - How fast it evolved and remained dominant That being said, there is a potential positive feedback loop going on, where most life depends on or benefits from compounds it gets from other life. Because there is an abundance of certain types of amino acids, we could hypothetically be stuck in a less optimal overall biosphere state, whereas a more fit biosphere might exist with a different composition of amino acids or other building blocks that played the same role. I'm defining fitness of the biosphere as the amount of energy from the sun that life harnesses for work. [0] https://en.wikipedia.org/wiki/Convergent_evolution https://en.wikipedia.org/wiki/Convergent_evolution

hypertele-Xii 4y ago
> There are so many examples of convergent evolution [0] here on Earth that it seems reasonable to speculate that many of the most useful compounds for life would evolve similarly many times over a large number of trials/planets. Examples of convergent evolution of the most useful compunds for life on Earth. It makes sense that in a unified environment (of Earth) there is a tendency to evolve similar mechanisms to survive - on Earth. But we just don't know what kind of other chemical environments might be out there, in the virtually infinite cosmos. As beings of Earth-based life we fail to imagine any other possibility. This is a failing of our own understanding, not of chemistry to produce life. We just don't know, so we can't really even begin to guess. All we know is, our own backyard looks pretty dead except for us.
- lend000 4y ago
  We can actually get a pretty good idea from looking at the spectral emissions, at least which environments are likely to be more common. On ptable.com [0] you can compare the abundance of elements in a human to the abundance on Earth, meteors, the solar system, and the universe. It seems like despite an abundance of aluminum, silicon, iron, and titanium, relatively trace amounts are found in humans (a typical animal), and most heavier elements are not needed at all and are actively toxic. The more versatile, modular, lightweight elements are very highly represented in humans. There's a reason organic chemistry is its own field -- those "more elementary" elements are simply more unique than heavier ones. At the top of the periodic table where the nuclei have small masses and closer orbitals, the relative impact of unfilled orbitals is much more significant. The standard reduction potential of Lithium (element no. 3) is a prime example of why it is so uniquely dominant for battery chemistry. I agree with you that our universe is a big place and a lot could happen, but my point is that attractor states exist and I would expect orders of magnitude more life to be based on organic chemistry, and probably even similar amino acids / a DNA double helix than not. Those lighter elements also tend to be more common elements throughout the universe, so the amount of planets where life with some inferior chemistry based on germanium (everything would be much heavier for the same reactivity patterns as an organic compound) would be limited to planets where there is a ton of germanium and not much carbon or silicon, which would be very rare (although it would be awesome to see what would happen!). [0] https://ptable.com/?lang=en#Properties/Abundance/Human https://ptable.com/?lang=en#Properties/Abundance/Human
  - hypertele-Xii 4y ago
    Seems very quantity-oriented. Maybe having lots of a thing is required for life to evolve from it, but again we have a sample size of 1. Maybe there is a quality-based form of life where what matters is not how much stuff there is to evolve from, but having a specific variety of different elements in the right conditions. Maybe all it takes is a handful of atoms in a particular unimaginable environment.

hypertele-Xii 4y ago

> There are so many examples of convergent evolution [0] here on Earth that it seems reasonable to speculate that many of the most useful compounds for life would evolve similarly many times over a large number of trials/planets. Examples of convergent evolution of the most useful compunds for life on Earth. It makes sense that in a unified environment (of Earth) there is a tendency to evolve similar mechanisms to survive - on Earth. But we just don't know what kind of other chemical environments might be out there, in the virtually infinite cosmos. As beings of Earth-based life we fail to imagine any other possibility. This is a failing of our own understanding, not of chemistry to produce life. We just don't know, so we can't really even begin to guess. All we know is, our own backyard looks pretty dead except for us.

lend000 4y ago
We can actually get a pretty good idea from looking at the spectral emissions, at least which environments are likely to be more common. On ptable.com [0] you can compare the abundance of elements in a human to the abundance on Earth, meteors, the solar system, and the universe. It seems like despite an abundance of aluminum, silicon, iron, and titanium, relatively trace amounts are found in humans (a typical animal), and most heavier elements are not needed at all and are actively toxic. The more versatile, modular, lightweight elements are very highly represented in humans. There's a reason organic chemistry is its own field -- those "more elementary" elements are simply more unique than heavier ones. At the top of the periodic table where the nuclei have small masses and closer orbitals, the relative impact of unfilled orbitals is much more significant. The standard reduction potential of Lithium (element no. 3) is a prime example of why it is so uniquely dominant for battery chemistry. I agree with you that our universe is a big place and a lot could happen, but my point is that attractor states exist and I would expect orders of magnitude more life to be based on organic chemistry, and probably even similar amino acids / a DNA double helix than not. Those lighter elements also tend to be more common elements throughout the universe, so the amount of planets where life with some inferior chemistry based on germanium (everything would be much heavier for the same reactivity patterns as an organic compound) would be limited to planets where there is a ton of germanium and not much carbon or silicon, which would be very rare (although it would be awesome to see what would happen!). [0] https://ptable.com/?lang=en#Properties/Abundance/Human https://ptable.com/?lang=en#Properties/Abundance/Human
- hypertele-Xii 4y ago
  Seems very quantity-oriented. Maybe having lots of a thing is required for life to evolve from it, but again we have a sample size of 1. Maybe there is a quality-based form of life where what matters is not how much stuff there is to evolve from, but having a specific variety of different elements in the right conditions. Maybe all it takes is a handful of atoms in a particular unimaginable environment.