And suddenly, BOOM, THE CAMBRIAN (pub. November 29, 2024)
A quiet week, two races back from the half-marathon, still enough time to wander.
Suddenly, more than 540 million years ago, multicellular organisms appeared, and they not only appeared in quantity but also in variety. The question is, why do so many critters appear so suddenly?
The truth is, I think it was not so sudden, we are talking about many millions of years ago, and as long as organisms with rigid structures did not appear, the possibility of them fossilizing was very low.
But, even so: what determined that such a great diversity of life appeared in such a short period?
The truth is that nobody knows. Let's wander...
The concentration of oxygen in the oceans and atmosphere increased until reaching values greater than 10% of the current level; This surely had an important weight. Aerobic organisms, taking advantage of oxygen, oxidize food by using oxygen more efficiently. It sounds like a mouthful, but that's how it was, obtaining more energy.
In addition, food chains, more correctly, trophic structures, were developed. The primary producers, bacteria and algae at that time, were eaten by some bugs that did not carry out photosynthesis. In addition, other bugs appeared that ate the latter. With this began the game of the hunted and the hunter.
This generated pressure to team up and colonies began to form from single-celled organisms. In them, some members began to adapt to fulfill specific functions, be it feeding, reproduction, defense, or attack. At what point does a colony stop being a colony and become a multicellular organism?
I don't know, there are colonial organisms that are very complex, and the specialization of their members is amasing.
But 600 million years ago: there were already multicellular organisms, the Ediacara fauna. These organisms were characterized by lacking rigid structures; some were ancestors of the organisms that appeared in the Cambrian, but most of them disappeared. As we mentioned before, lacking rigid structures, their fossilization was more difficult and that is why they left less trace. But every day more information appears about them and they were already very varied
Anyway, it is surprising how suddenly not only a huge variety of organisms, but a huge number of rigid structures appeared. Many for defense, many for attack.
The development of rigid structures requires the use of energy. As I said, they were already more efficient at obtaining energy from food, being able to provide extra for these rigid structures. Weathering on land above sea level must also have somehow increased so that minerals were abundant in ocean waters.
I assume that the first rigid structures were simply so that some organisms could “scratch” solid surfaces covered in bacteria and algae and feed more efficiently. From there it only took one step for these structures to be used to feed on other animals, which made it profitable to form shells to protect themselves. Already with rigid structures they could have appendages to move faster and search for prey or flee from hunters.
And if I'm looking for someone to eat or someone to hide from, who wants to eat it, sight is essential, which is why the eyes begin to appear.
In this competition between prey and predator, some organisms specialized to defend themselves from who wanted to eat them or to eat whoever gave them the most benefits; also to look for how they would have more benefits; They sought to reduce who they could compete with. Generating a great diversity of living forms in a short time (in geological terms).
Anyway, not only does a great diversity of critters appeared, but also the groups of animals that continue to exist. I don't mean to say that the animals and plants that we know now were already there, but the ancestors of those of us who are here now were already there.
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