HAS HUMAN EVOLUTION STOPPED?
Early humans first migrated out of Africa into Asia probably between 2 million and 1.8 million years ago. They entered Europe somewhat later, between 1.5 million and 1 million years. People first came to Australia probably within the past 60,000 years and to the Americas within the past 30,000 years or so. The connectivity of today’s world means we are all growing together now. But does that mean that human evolution has stopped?
There are arguments for both cases but no definite conclusion. This article does not intend to start an endless debate between the two parties. The aim of this article is to make sure that we think at least once the next time we decide to let a smartphone make a decision for us.
How do you define Human Evolution?
First of all, let’s understand what evolution is. Evolution deals with selection or adaptation, which results in populations of organisms genetically different from their ancestral forms. Human evolution does not mean progress. That means that the latter generation may not be necessarily more advanced than their predecessor.
Now let’s explore some arguments that support both hypotheses.
Yes, We Have Evolved!
In 2010 the size of a skull that belonged to a Cro Magnon man was measured and its size was found to be 1350cc. The size of the brain of an ancient ancestor was found to be 1500cc. The brain of Homo Erectus, an ancient human species millions of years ago, had a brain of size 1,100 cc. The research clearly suggests that the human brain is getting smaller.
But does that mean that a bigger brain means more intelligence? Scientists try to support the idea that we are more intelligent than our ancestors. So they try to disconnect the size of the brain with intelligence but there is no way to prove it since we can’t measure the intelligence of ancient people even if we had a way of doing that.
In developed and developing countries children who have been exposed to electronic gazettes find it difficult to withdraw. Photo by Thanasis Zovoillis via Getty Images.
Even though we can’t measure intelligence, some things are evident – like that fact that we choose to rely on our navigational system to get from A to B rather than memorizing the routes or the fact that we don’t remember most of the phones numbers in our address book.
The things that we accomplish in daily life are somehow dependent on technological advancements. But does accomplishing those things really make us intelligent?
A hypothesis was published in the Cell Press journal Trends in Genetics by Dr. Gerald Crabtree of Stanford University. He suggests that our brain power might be susceptible to dumbing down mutations which might lead to us losing our intellectual and emotional capabilities.
Dr. Gerald Crabtree also assumes that in the future we might be able to fix the mutations using science and medicine and removing the process of natural selection altogether.
Sir David Attenborough, in one of his articles, said he believed humans had now stopped evolving in physical terms. He said that because we have developed means to keep even the weakest of the species alive. Saying we are now able to rear up to 99 per cent of our babies, he added people were no longer subject to Darwinian theories natural selection.
Instead, Sir David Attenborough proposed, humans would continue to develop in a cultural sense by inheriting knowledge from previous generations.
Sir David Attenborough. Photo source Wikipedia.
The ability to cook food provides humans with a greater dietary flexibility than chimpanzees, gorillas or orangutans. This dietary flexibility has allowed humans to survive in a greater range of environments. Humans also show greater flexibility which increases our ability to survive short-term environmental fluctuations.
We have greater variation in fertility, which allows populations to bounce back quickly after periods of high mortality. All of these physiological features allow us to respond to environmental stress without the need for genetic adaptation by natural selection.
No We Haven’t Evolved!
There are examples of human evolution that occurred subsequent to the invention of agriculture. They involve the co-evolution of cultural and genetic systems with changes in subsistence strategies.
The example that is most often cited is the natural selection of heterozygous carriers of the sickle-cell gene to maintain sickle-cell anaemia in populations that are exposed to malaria. This natural selection is particularly visible in regions of central Africa where tropical forests have been cleared for agriculture.
Thomas Malthus was worried about the rising population of the lower classes in early 19th century England. If a population grows too large to be supported in its habitat some individuals must die before they reproduce. But Charles Darwin reasoned that if survival depends upon physical traits and if those traits are passed on from parent to offspring, then those with more favorable traits are more likely to survive and reproduce.
This led to the birth of Darwin’s principle of natural selection.
Some pathogens continue to exert challenges on modern medicine by becoming resistant to drugs like HIV.
Fertility differences have become marked in today’s industrialized societies, as people delay starting families into their 30s or 40s.
Even though infant mortality has made much progress in combating diseases yet children’s survival is not assured. Around the world a lot of people lack access to basic healthcare.
Research also shows some genetic variation among humans like the capability of digesting milk through lactase which arose about 6000 years ago in Europe. It later evolved independently, through mutations in different genes in separate pastoral populations in Africa.
Climate, weather, geological processes, disasters, infectious diseases, parasites – these are just some of the things that affect our evolution through natural selection.
It’s evident that human evolution is still taking place around us both physically and culturally. Whether it’s making us smarter or dumber, stronger or weaker is every man’s opinion. Today the whole world is connected by technology. There is no isolated island left on its own to grow as it will. Hence, we can’t have a gross evolution that can give us a big brain and a strong body.
The only way such an evolution can be achieved is through genetic engineering but that’s decades from now. For now we are the only means of making ourselves smarter and stronger.
Deepti Chauhan graduated in Computer Science from Delhi College of Engineering after which she worked with Samsung as a software developer for 2 years. Deepti joined Earth5R to build changes that she wanted to see around herself, for the society and for the planet. She feels that to change the world we should start changing ourselves.