Cells are the smallest unit of life that are classified as living things.  Humans are made up of trillions of cells, which are essentially animal cells.

Have a read of the following article (courtesy of our resident IntoScientist and passionate educator, Dave Canavan) which outlines the “molecular clock” and how human beings have evolved over time.

IntoScience human evolution

Human Evolution

If we were to put naked humans in an enclosure in a zoo and we had alien scientists visit Earth, there would be no doubt the humans would be classified as a very close relative of chimpanzees and bonobos. They would potentially be placed within the same genus. To put this in perspective, lions and tigers share the same genus, and can even interbreed.

The similarities between chimps, bonobos (often referred to as pygmy chimps) and humans is striking. Their physiology is extremely similar, which leads to many humans saying, when having the pleasure to meet a chimp or other ape: “Aren’t they so human like?” They have individual fingerprints and the same blood types as humans. You can legitimately have a blood transfusion from a chimp and be perfectly fine.

But the real similarity with chimps and humans is in the cells. DNA, the four-based code that is present in all life, is astoundingly similar in humans and chimps. We share at least 98.5% of our DNA with chimps, although recent studies suggest that figure is up to 99.4% when studying critical DNA. This alone is evidence that we are very closely related to chimpanzees and bonobos.

What is also interesting is that based on this molecular evidence, the split between humans and chimps, and humans, chimps and gorillas, our next nearest relative, is greater, where humans and chimps share approximately 97% of DNA with gorillas. That means that chimps are more closely related to humans than they are to gorillas!

The Split

One common misconception of all this information regarding human/ape similarities, is that people often ask why chimps aren’t still evolving into humans? The answer is simple: humans never evolved from chimpanzees in the first place.

Chimps and humans evolved independently from a common ancestor. Chimps, although relatively unchanged, are perfectly adapted to live in the jungle and survive so much better than any human would. Conversely, humans are much better adapted to live on the savannah, where chimps would struggle.

Based on the fossil record and a ‘molecular clock’, we know the split from common ancestry to be somewhere between 4 and 7 million years ago. This is when humans and chimps took their separate paths of evolution.

The molecular clock is based on a steady mutation rate. If you take the DNA that comprises haemoglobin which is present in all vertebrates and therefore has been part of our DNA for many millions of years, you can see mutations that have happened in the DNA sequence yet leave the molecule fully functioning.

These mutations happen at a steady rate when analyzed over millennia, and therefore the differences in DNA in structures such as haemoglobin can give us an approximate time as to the relatedness of species, if you know how often these mutations happen.

The Fossil Record

The most compelling and overwhelming evidence for human evolution is the fossil record which shows transitional fossils of ape-like humans, through to more modern humans and finally us, Homo sapiens.

In 1856 in the Neander valley in Germany, workers uncovered a skull that was kind-of human like, but still very different. It had a sloping forehead, heavy set jaw and very prominent brow ridge. A notion of a half-human half-ape like creature was considered but the fact that it could be an ancestor was not really accepted.

Then, in 1859, Charles Darwin published On the Origin of Species, which transformed the way in which people viewed evolution and how species diversity came to be. This was the platform on which human evolution grew, and with the discovery of more intermediate fossils, human evolution had overwhelming evidence.

Many key factors are integral as to how humans evolved. These are the coming out of the trees, then walking upright (bipedal) which frees the hands to allow tool and weapon use, language development and culture. There are many ecological reasons as to why these advancements happened but exactly when is unknown.

When Lucy was discovered, (named after the Beatles song ‘Lucy in the Sky with Diamonds’), this answered at least one of these questions. Lucy was a bipedal (upright walking) ape-like ancestor and existed about 3.6 million years ago. She is of the genus Australopithecine which are the most ape-like of our ancestors, although their skulls and teeth were certainly becoming more human-like.

The Australopithecine genus diverged off our evolutionary past and eventually became extinct, with other transitional fossils leading to our path. As the hominids became larger bodied with larger brains they became classified in the Homo genus. There have been many Homo ancestors of humans but the most notable are H. neanderthalensis (of which the Neander Valley discovery lent its name) and H. erectus.

Out of Africa

Homo erectus was the first human ancestor to leave the cradle of humanity, Africa, and did so about 2 million years ago, spreading throughout Asia and Europe. Later, around 600,000 years ago, Neanderthals evolved and spread throughout Europe.

Meanwhile, approximately 200,000 years ago the ancestors of you, me and every other human on Earth evolved in Africa, finally becoming Homo sapiens: wise man.

Around 50,000 years H. sapiens left Africa and spread throughout the old world. They superseded erectus in Asia, and about 30,000 years ago finally saw off the last of the Neanderthals to remain the only human species of animal left.

Since that time, tool use and technology has continued to advance exponentially. Art, in all its forms, has progressed from the meagre cave wall paintings to the Sistine Chapel ceiling. Agriculture and domestication have literally changed the world and language has developed into the written word.

We have certainly come very far in the last 50,000 years but we mustn’t forget our history and heritage, on which all our successions are based. All humans on Earth are of the exact same species, despite color, race or religious belief. As Jared Diamond, a respected biologist once stated: we are simply the third species of chimpanzee.

Biological classification places chimps and bonobos into the genus Pan, but if biological classification rules were correctly applied regarding species relatedness, the reclassification of the three chimpanzees should be Homo sapiens (humans), Homo paniscus (bonobos) and Homo troglodytes (chimpanzees).

Read more of Dave Canavan’s articles here :  www.thechingchokhunter.com