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Comment by dogma1138 | Hacker News Reader

Before people jump to conclusions panspermia really only matters if a) life and its components is extremely rare and/or b) the creation of the precursors for life has to happen in space.

There is strong evidence to suggest that life have started on earth multiple times, it’s nice we find amino acids and other complex compounds on small rocks in space but it would only matter if these compounds somehow don’t form on much bigger rocks like planets.

So the evidence we collected from asteroids and comments so far mainly suggests that the components needed for life can and do form pretty much anywhere at least in our solar system.

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One really fascinating thing is that the earliest known life we have on Earth is unexpectedly complex in terms of its DNA. If one looks at how the complexity evolved to modern day, and then ectrapolates backwards, it looks like the DNA would have been pretty simple around the time when the universe was still reasonably warm. So, it could have happened that very simple lifeforms formed on somewhere in the early universe and arrived on Earth on asteroids.

Kurtzgesagt did a nice video on thus recently. I always thought panspermia was totally ridiculous theory, but there are some nice arguments behind it.

Just so we're all clear, no one has any idea how life could have emerged on Earth without external help.

It's a long way from amino acids to life -- like the distance between the squiggles that make up the letters of the alphabet and Milton's Paradise Lost.

I mean, why not just declare Carbon, Hydrogen, and Oxygen to be "precursors for life" and then declare "the ingredients were already there!"

For those who are genuinely interested, check out the book The Stairway to Life: An Origin-of-Life Reality Check by Tan & Stadler.

There's quite a number of different theories for how life could've emerged on Earth.

Currently most popular, as I understand it, is the hydrothermal vent hypothesis, which uses the energy gradient provided by the heat from underwater hydrothermal vents as the motive power for the kind of self-assembly required and uses things like RNA, which still today creates its own transcriptive mechanism as well as several other utility enzymes, but the basic requirement is an energy gradient - beyond that, an awful lot of the chemical precursors to life seem to be self-assembling in the right conditions.

Now, if you want to argue about where exactly that transitions from self-propagating chemistry to actual Life occurs, that's a question for the philosophers - things get a bit muddy at that scale, but mechanistically, I'm not aware of a "missing link" in the early story of life.

I'm sure that if we put the word out we could get another two dozen theories.

But "science" needs to mean more than "speculative theories that adhere to my philosophical presuppositions".

Right, usually it's "speculative theories that we can assemble evidence for by building upon prior work and known facts about the world", which the hydrothermal vent theory is. "Science" when talking about "how did life form" will always be "speculative theories" until we crack the time-travel nut.

Science also requires a plausible mechanism and an understanding of statistics. "It must have randomly happened even though the chance was less than 1 in ten to the five hundred and twelfth" is about as far as these speculative theories have gotten so far.

The entire field of biology rests on the maxim that improbable things become probable with enough time and opportunity.

It has to be grounded in statistical reality. What do you think the sum total is of all the organisms that have ever lived on Earth?

Interesting looking book. I'll have to check it out. In my experience, discussing this material online tends to devolve into an atheist/theist debate. Both sides are very sure of themselves and it isn't about exploration and curiosity so it tends to turn off us more agnostic-minded people (or just those both open to abiogensis as well as other creative possibilities).

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