Do you know why we are humans?

Prof. Know Why answers:

This heading, “why we are humans” may sound weird, unless explained. There are so many different species living on earth, some, even being gigantic and physically immense powerful, but we, humans rule the planet Earth, in spite of being so tiny little beings! We have either tamed all the fierce and threatening species or put them in enclosures according to our whishes and requirements. And only we study them through various researches and it’s not the other way round. All these prove that we are the most powerful of the species. What makes us supreme? It’s sheer intelligence!

But why and how are we humans more intelligent than others? Researches have proved time and again, that it’s all in the brain. We humans have more advanced and bigger brain. When comparing different species, brain size does present a correlation with intelligence. For example the ratio of brain weight to body weight for fish is 1:5000; for reptiles it’s about 1:1500; for birds, 1:220; for most mammals, 1:180, and for humans, it’s 1:50. Modern studies among people, using brain scans have shown that brain size shows a rough correlation with IQ among adults of the same sex. The brain is also a metabolically expensive organ, and consumes about 25% of the body's energy.

Recently, scientists have identified a gene that controls the size of the brain, a finding that will give an insight into what it means to be human. The research team in Edinburgh has found that when the newly identified gene is faulty, the brain and body shrink as a result. Dr. Andrew Jackson and colleagues at the MRC Genome Damage and Stablity Centre studied families who have members with Seckel syndrome that retards growth in the womb, leading to short stature and a markedly reduced brain size (microcephaly).

The study noted that small brain size is linked to faults in a gene called PCNT. This gene works with another gene linked to the condition called ATR, which is again involved in DNA repair. The PCNT gene is responsible for the manufacture of a protein in the body called pericentrin, a component of the centrosome that is essential for the process of cell division that underpins growth. Other genes involved in the working of the centrosome have previously been found to be mutated in different forms of microcephaly, suggesting that it is essential for determining brain size.

So, it’s the size of the brain which is controlled by gene that makes us human, as larger brains and not bodies are associated with higher intelligence.

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