Top 10 scientific mysteries about the origin of the first humans
Humans are unique creatures among the life forms on this planet. Although Charles Darwin's Theory of Evolution, supported by the discovery of several fossils, has contributed to understanding some crucial questions about the origin of Homo Sapiens Sapiens, many aspects of its evolution still remain a mystery.
What were the stages of the long process that led to the appearance of Homo Sapiens on planet Earth? And what is their chronological order?
Why did we evolve this way and not in another direction? Why are we the only human species left? What happened to the Neanderthals?
In short, a series of questions that make the discoveries obtained so far just a drop in an ocean yet to be explored. Currently, the study of the evolution of humankind represents, in both theoretical and methodological terms, an extremely diversified and heterogeneous sector.
The study of morphology and anatomy makes use of digital techniques, with applications that include computerized tomography, virtual image processing, artificial intelligence and geometric modeling of structural components.
Many sectors of biology have been strengthened or added to evolutionary disciplines, such as paleoneurology for the study of brain structures or paleohistology for the study of fossilized cellular traces.
Genetic and molecular analyzes are able to extract DNA going back in time to around 40 thousand years ago. Direct and indirect dating techniques follow the evident updates of physical and chemical disciplines. Finally, archeology subjects its historical information to experimental verification.
If you think about it, the fact that man is the object of study of man himself represents a rare anomaly. Compared to other scientific disciplines, in anthropology man is both an object of study and a studying subject.
10. Why did we develop such large brains?
There is no doubt that our large brains have given us an extraordinary advantage over other living species on the planet.
The human brain is an extraordinarily expensive organ: it occupies only 2% of the body's mass, yet uses more than a fifth of the energy produced by the body.
According to researchers, until 2 million years ago, none of our ancestors had a large brain. What started the growth of the brain organ? One hypothesis is that the brain grew to give our ancestors the ability to make better tools.
But this is a consequence of growth, not the cause. Another hypothesis is that larger brains contributed to improved social interaction, favoring the development of more complex social groups.
Finally, it cannot be ruled out that the radical environmental changes that occurred in the Earth's past may have contributed significantly to the growth of brain functions, so much so as to allow our ancestors to adapt to a climatically changing world.
9. Why do we walk on two legs?
Our ancestors developed upright postures long before our large brains, and developed the ability to make tools. The question then is why do we stand when our ape cousins move using four limbs?
Walking on two legs could mean less energy expenditure. Furthermore, the use of the arms may have allowed easier retrieval of food.
The most shared theory among researchers is that bipedalism developed as an adaptation to the progressive disappearance of large rainforests and the advance of prairies, forcing primates to abandon arboreal life. This process would have occurred about 6 million years ago.
But this automaticity has been called into question by a recent geological discovery which places the retreat of the forests at 12 million years ago. This means that there is a discrepancy between the geological data and the fossil findings, forcing us to identify another factor that favored the development of bipedalism.
8. What happened to our hair?
Compared to other primates, humans are the only ones to have lost almost all of their hair. Why this nudity? Also in this case there are many hypotheses proposed. One possibility is that our ancestors shed their fur to better withstand the heat experienced while crossing the African savannah. Others propose that the fur was lost to better defend against parasites and diseases.
An unorthodox idea suggests that human nakedness developed after our ancestors briefly adapted for aquatic life, losing their hair to decrease friction during deep swimming. It is the theory of aquatic humanoids proposed for the first time in 1930 by marine biologist Alister Hardy.
7. Why did our closest relatives become extinct?
About 24 thousand years ago, our species, Homo Sapiens, was not alone on the planet, but shared natural resources with Neanderthals, our closest relatives.
Have paleoanthropologists also discovered the existence of a small hominid, called 'hobbit' in the wake of the 'Lord of the Rings' saga, who lived in Africa about 12 thousand years ago? What happened to them?
Was it an infection or rapid climate changes that led to the disappearance of the other homos? Or, was our species so invasive that it generated the conditions for it to disappear from the evolutionary scenario? Some evidence supports both scenarios, but neither conclusion is widely shared by researchers.
6. What is the hobbit?
The hobbit, nickname given to the small skeleton found in 2003 on the Indonesian island of Flores, is an extinct human species, whose official name is 'Homo Floresiensis'.
Researchers have wondered whether they are a true hominid species, or whether they are deformed human individuals. The evidence shows that it is a different species from ours.
It probably coexisted with Homo Sapiens. The traits of this hominid are halfway between those of the first hominids and modern Homo Sapiens.
It was just over a meter tall, and with a cranial capacity of 380 cm3, much smaller not only than its contemporaries but also all known hominids that preceded Homo sapiens, including chimpanzees and gorillas.
Unfortunately, the hot and humid climatic conditions of the excavation area are unfavorable for the conservation of DNA, and the attempts made so far to collect analyzable genetic samples from the finds have failed.
5. Why is human evolution so fast?
Some recent studies have shown not only that humans are still subject to evolution, but that it is actually accelerating, up to 100 times the levels recorded since the appearance of agriculture.
A number of scientists, challenging the strength of this evidence, say it remains difficult to ascertain whether some genes actually grew that fast. Among other researchers, however, there is a certain dismay when considering the extremely limited space of time in which the human species evolved.
To make an undue comparison, we can think of dinosaurs, a group of living beings that dominated planet Earth for 160 million years, an extremely long biological life cycle or, at least, in harmony with the cosmic times of the Universe.
If human evolution happens so fast, the question is: why? Diet and disease could be some of the factors that have caused this rapid evolution, but nothing certain has yet been found in this regard.
4. Why did modern man leave Africa?
At a certain point in its evolutionary history, Homo Sapiens left Africa about 50 thousand years ago, to spread throughout most of the world's emerged lands, reaching as far as the most remote islands of the Pacific, colonizing all the continents except Antarctica.
A number of scientists believe that this migration is linked to a mutation that occurred in our brain, which led to the capacity for complex use of language and the design of more complex tools.
The most widely accepted theory is that hints of this modern behavior existed long before the migration began, and that humanity decided to leave Africa due to the growing number of individuals and the scarcity of available resources.
3. Did we have sex with Neanderthals?
Did Homo Sapiens interbreed with Neanderthals? Are there genetic residues from our closest relatives in our DNA? Some scientists say that Neanderthals did not become extinct, but were absorbed into modern humanity.
Recent research from the University of Montreal firmly established that Neanderthals and humans interbred sexually after migrating from Africa between 50,000 and 80,000 years ago.
And this piece of DNA, which is found on the human X chromosome and reminds us of these past relationships, is present in 9 percent of humans worldwide, except Africa.
2. Who was the first hominid?
Scientists are discovering that the origin of men is increasingly ancient. The effort is to find the fossil of the first hominid, direct ancestor of modern Homo. Recent studies reveal that almost every man currently alive can trace his origins back to a single hominid who lived around 135 thousand years ago. This man can be considered the 'mother of all humans', practically demonstrating the existence of what the Bible calls 'Adam and Eve'.
This discovery, from a team led by Carlos Bustamante, geneticist at Stanford University, California, come from one of the most complete analyzes ever carried out on the male chromosome (Y), which is passed down from father to son, in order to be able to identify mutations and trace the male line back to the progenitor of all human beings. The findings overturn previous research, which suggests that the common ancestor of all humans is much older than the 50,000 years previously assumed.
1. Where modern humans came from
But the most hotly debated question in the theory of human evolution is where modern humans most likely evolved. The classic hypothesis holds that Sapiens evolved recently in Africa, and then spread throughout the world, replacing archaic Homo populations.
The multiregional hypothesis, however, maintains that humans evolved over a vast geographical area, descending from archaic hominids, mating with them and sharing part of the genetic heritage. The Africa hypothesis currently enjoys the favor of a large number of scientists, but supporters of the multiregional hypothesis remain steadfast in their beliefs.
