In the process of biological evolution, human beings can be regarded as lucky, and early humans did not encounter the era of dinosaurs and crocodiles, nor did they encounter any instantaneous devastating disasters.
It is even more fortunate that the human ancestors chose the right direction of evolution from the beginning, focused on evolving their own brains, and only took seven million years to evolve themselves from the ancient apes that could initially walk on two legs to the modern humans who can now produce such advanced technology.
Compared with humans, carnivores always evolve in the direction of improving their muscle strength, body size, bite force, etc. more suitable for hunting, and herbivores always evolve in the direction of running faster, thicker skin, etc. to make themselves not easy to be eaten, after all, in nature, survival is the first priority, and to ensure survival is to ensure that they are not hunted while having food.
Only humans, instead, chose to evolve their own brains to do this extremely energy-intensive and seemingly useless thing. Because as the size and weight of the brain increases, human physical fitness becomes weaker and weaker.
Now, with the physical fitness of human beings, they can only eat berries in the wild to fill their hunger. The fragile intestines, not so sharp teeth and very poor immunity, even let us not even eat the stream and raw meat for three consecutive days, lack of houses, clothing warmth, the cold of the night we can not last long.
So how did the human ancestors survive during the extremely harsh Quaternary Ice Age?
The Quaternary Ice Age, which occurred 2 million to 3 million years ago and ended 10,000 to 20,000 years ago, is also occurring during the rapid evolution of human beings.
Between 3 million and 4 million years ago, Australopithecus appeared, and most scientists now refer to Australopithecus as "a man on the way" and believe that modern humans developed from one of Australopithecus.
When Australopithecus appeared, the Earth had not yet entered the ice age. Their brains are only one-third of that of modern humans and are about 450 cubic centimeters in size. It has curved fingers and toes, flexible and long arms, and lives mainly in trees. But the leg bones are bent inward, indicating that they are already able to walk on two feet.
After the Earth entered the ice age, Australopithecus advanced into Homo erectus.
Homo erectus existed 200,000 to 2 million years ago, which was quite a long time in the evolution of ancient apes.
Compared to Australopithecus, homo erectus has changed dramatically. They learned to stand up straight and walk, which is why they are called "Homo erectus", and their retrocranial skeleton developed very similarly to that of modern humans.
Australopithecus's lifestyle was still primitive, but Homo erectus had learned to use simple tools to kill some animals and feed themselves meat. Bipedal walking gave Homo erectus better endurance, and they would drive their prey exhausted and kill them with simple tools.
Before Homo erectus ate meat, their brains were about 850 cubic centimeters in size, and meat provided Homo erectus with a lot of energy, and the brain began to develop towards larger, heavier structures and more complex structures.
It was also at this stage that Homo erectus encountered predators, cats, represented by saber-toothed tigers.
In terms of size and combat effectiveness, saber-toothed tigers and other mammals are actually inferior to the previous overlords dinosaurs and crocodiles, so it is said that humans are still relatively lucky in evolution. The opponent is strong, but it is not too strong to be invincible. If the opportunity of human evolution is really cast into the age of dinosaurs, it is estimated that it will be extinct before a stronger brain is evolved.
How did human ancestors survive the cold and powerful predators of that period?
During the Ice Age, much of Eurasia and North America, temperatures were below -20 degrees Celsius in winter and below freezing in summer. In today's Russian region, Europe, and northern North America, temperatures are below minus forty degrees Celsius in winter and minus ten degrees in summer.
But in Africa and South America, near the equator, temperatures have always remained above ten to twenty degrees, but even this temperature is still a bit cold for humans today, because humans have faded almost all of the most important things in animals in the process of evolution - body hair.
It just so happens that most scientists believe that human body hair faded 1.5 million years ago, during the glacial period.
To resist the cold and lose body hair, the ancestors of the human race at that time learned to use fire, and it just so happened that fire could burn back the beasts, and the meat that had been burned by fire was less likely to make humans sick, because the bacteria and parasites on the meat were burned.
The use of fire is a huge advance in the history of human evolution.
Between 30,000 and 200,000 years ago, human ancestors evolved into Neanderthals, and some reasons for humans to resist the cold can also be found from Neanderthal bodies.
Neanderthals had wider breasts than modern humans, were more funnel-shaped, were shorter but stronger, and had a larger nose, which filtered out the heated dry and cold air. This body structure is somewhat similar to that of people who now live in cold areas and can help them retain heat.
Using tools to heat, eating meat to store heat, and restructuring their bodies to adapt to the cold, Neanderthals endured the cold of the ice age through these. During this period, the Neanderthal brain developed as large as that of modern people, or even larger.
In addition, in the face of natural enemies big cats, the human ancestors at that time actually had no way to deal with these large beasts, if a person encountered outside, it can be said that they must die.
Fortunately, at that time, people had learned to use tools, and lived together as small families, some people were responsible for guarding, some people were responsible for hunting, some people were responsible for picking berries, some people were responsible for maintaining the comfort of the living environment, and so on, even the division of labor and cooperation.
Such a way of life, although it can not defeat the saber-toothed tiger, but the good villain can reduce casualties.
And through the Neanderthal ankles, they are not suitable for long runs, more suitable for ambushes, and strong and flexible arms are suitable for throwing spears, which can help them ambush large prey, and of course can also be used to defend against predators.
With a series of life-saving means, human ancestors survived until the extinction of saber-toothed tigers, which was 10,000 years ago, and the ice age was basically over. Large, lethal mammals were largely extinct, and the most ferocious animals on land at this time were tigers and lions.
At this time, the development of the brain allows human beings to have language, can create and invent more simple and practical tools, and create human society. After only a few thousand years, it completely raised its eyebrows and breathed out, and carried out a century-long tiger fight against the big cats that forced human ancestors to only dare to hide in the hole, which was considered to be revenge for that year.