A few million? Absolutely not. We can trace continuous lineages connecting all living things on earth to each other, and to ancestors hundreds of millions of years ago.
Could early single celled organisms have come from an asteroid? Perhaps, but almost certainly not. It is strictly less likely than Earth-bound abiogenesis. Life still had to spring from nothing somewhere - all panspermia does is layer on an additional series of long-shot coincidences.
> It is strictly less likely than Earth-bound abiogenesis
> all panspermia does is layer on an additional series of long-shot coincidences
Disagree. There is a lot more of not-Earth than Earth. I agree that the probability density (per unit volume of the universe) of life originating on Earth is much higher than anywhere else, but there's just so much more room out there for life to originate that the probabilistic cost of traveling to Earth is tiny in comparison.
All you need is a proto-life that's stable in an inert environment with sufficient radiation shielding. It could've originated billions of light years away and still have had enough time to arrive on Earth 4.2 billion years ago. That's a mind-boggling number of Earth-like environments.
In fact, proto-life doesn't even need to look like Earth life, so even environments that are hostile to current Earth life today could've been the cradle of origin (as a wise man once said, "life, uh, finds a way"). Additionally, environments that used to be Earth-like but eroded away are candidates too since all we need is for life to have escaped before the erosion.
In my opinion, panspermia is strictly more likely than Earth-bound abiogenesis.
Kurzgesagt teached me that at some point between Big Bang and now, the universe had an average temperature equalling comfortable room temperature. Having realized that, it feels likely life could have formed basically anywhere.
I don't understand panspermia enjoyers. The Earth was just sitting there for a couple billion years; what sensibility of yours does it offend to accept abiogenesis occurred on it that you have to imagine weird impact ejecta delivery systems.
We are not such a simple thing that we should be the result of a simple random collision.
Like your body -everything is cut out according to its innate abilities with perfect measure and order, and put together with the finest art, in the shortest way, the best form, the lightest manner, and most practicable shape. Look at the clothes of birds, for example, and the easy way they ruffle up their feathers and continuously use them. Also, things are given bodies and dressed in forms in a wise manner with no waste and nothing in vain
Check out the giraffe's cardiovascular system. It seems you're alluding to intelligent design and there's a lot of very unintelligent "design" everywhere.
Tell that to the laryngeal nerve which loops around your aortic arch, for no good reason. And to our inferior eye compared to the octopus. Amongst other things.
> and put together with the finest art, in the shortest way, the best form, the lightest manner, and most practicable shape
Yeah nah. Ask any doctor or biologist. Humans and most other organisms are definitely not put together like that. It's pretty cool and it works very well, but many things are just... why? There's lots and lots of hacks, questionable cable management, backwards design, dead code, and leftovers from previous iterations.
Just because we're a pretty successful organism does not mean we are anywhere near the pinnacle of what can be achieved.
