archaeopteryx
Our mathematics is decimal now, why not ternary, octal or hexadecimal? Aristotle thinks that human beings adopt decimal system because they always have ten fingers. When people first began to know numbers, they actually counted and calculated them based on the number of fingers. It is the same as the hand index of kindergarten children who can do arithmetic problems now. The decimal-based counting system can be said to be the cornerstone of the whole human science and technology, which was laid by a competition among creatures 300 million years ago. At that time, we were still a fish.
Amphibians, reptiles, birds and mammals are all called "quadrupeds" because they all walk on four legs. Four-legged animals have almost all five toes, and even snakes are four-legged animals, but the feet of snakes later degenerated. In other words, almost all animals that live on the earth's land are quadrupeds with five toes.
Human hands, medieval European paintings.
In the late Devonian (about 350 million years ago), many quadrupeds had more than five toes, but it didn't take long for them to evolve into five quadrupeds with more than five toes, all of which were basically extinct. The cause of extinction remains a mystery. It is likely that five-toed quadrupeds have more advantages in walking and grasping, and gradually occupy the ecology.
The first quadruped on earth was born in the late Devonian 365 million years ago. Primitive quadrupeds evolved from fish, and all terrestrial vertebrates, including humans, evolved from fish.
How can we judge that our ancestor was a fish in shallow water 365 million years ago? It is mainly inferred from fish fossils and the structure of existing fish meat.
Meat fin fish 300 million years ago
The creatures that exist on the earth now did not suddenly appear at a certain moment, otherwise the earliest biological fossils should include birds, reptiles and mammals. The sequence of biological fossils in rock strata from simple to complex shows the correctness of the theory of biological evolution.
The earliest biological fossils on earth are microfossils found in Quebec, Canada. The microfossils were 4.28 billion years ago. In the long years after that, all living things only stayed at the stage of microorganisms, fungi and algae. From 635 million years ago to 542 million years ago, a large number of multicellular animals appeared on the earth, and from 546.5438 million years ago to 485 million years ago, the earth was again destroyed.
A portrait of Neanderthals reconstructed from fossils
423 million years ago, fish appeared in the ocean. One kind of fish is our ancestors. What were human beings like at that time? Now it's irreversible. We can only roughly imagine what human beings were like 400 million years ago according to the existing fleshfin fish. The total class of fishes includes coelacanth and tetrapod lungfish. Most fish on the earth are extinct now. Saury living in the western Indian Ocean and lungfish living in Africa are one of the only remaining species of coelacanth and tetrapod lungfish. Fleshfin fish is directly related to later amphibians and reptiles, and quadrupeds evolved from the four fins of fleshfin fish.
Fleshfin fish came ashore from the ocean mainly because the terrestrial ecosystem of the earth was very colorful 365 million years ago. There are a lot of wetlands near the coast and estuary delta. On the coastal beach, some branches of fleshy bone fish gradually evolved into quadrupeds. The reason why they travel near the beach and estuary delta is actually to survive and occupy an ecological niche that is not occupied by other animals. The earliest quadrupeds living on land appeared in the Carboniferous period (359 million years ago to 299 million years ago). However, at that time, quadrupeds could only stay out of the water for a while. These quadrupeds often needed to stir the mud in the beach with their fins. As a result, they often evolved for a long time before their fins evolved into limbs.
Dolphins return to the ocean, and their limbs evolve into fins again.
In a sense, the species from fish to amphibians are mudskippers. They live in coastal shoals and often catch insects on land in one leap, but they can't live on land for a long time.
Now all vertebrates on land were still a fish 360 million years ago, which is another important evidence that almost all animals need to drink water and replenish water regularly. Without water, it is difficult to survive, which means that although we leave the ocean, we still can't live without water.
The intermediate link in the evolution of marine animals to land animals is that these animals must first be able to survive in the estuary delta and coastal beaches on land.
Many quadrupeds that have just landed have more than five toes. Later, animals above five toes were basically extinct. Animals with six toes and eight toes may not be very flexible and gradually lose to animals with five toes in the competition. In this way, five toes occupy the mainstream, which is why we humans have five fingers.
From fish fins to quadrupeds' limbs.
Of course, after quadrupeds are unified into five toes, it doesn't mean that all five toes are unchanged and unnecessary. In order to run faster, the horses gradually merged into horseshoes. Now horses seem to run with one hoof, but in fact they have five toes. Now they can still see the traces of five toes on the horseshoe. In order to adapt to flight, birds' forelimbs evolved into wings, and their hind limbs stood better after landing.
Incredibly, 300 million years ago, the toes of quadrupeds were unified into five, which turned out to be a cornerstone of mathematics and natural science today, because some of the most basic units of measurement in natural science are decimal, and our counting system is also decimal. If it is hexadecimal, ternary or octal, maybe today's science is another scene.