‘Humans won’t go extinct; but they are at a crucial point’

Photo: iStock

The story of human evolution began seven million years ago when an ancestor common to humans and chimpanzees roamed Africa. Since then, hominins, a group consisting of our immediate ancestors walking upright, emerged.

Two million years ago, Homo erectus, a hominin with a human-like body arrived on the scene. Our species, Homo sapiens appeared only 200,000 years ago in Africa. Gradually, other human species died out. Evolution drove species to arise, adapt to the environment or even die out.

What shaped human evolution? Why did Homo sapiens thrive while other human species went extinct? What are humans likely to look like in the future?

Down to Earth spoke with Nathan H Lents, professor of biology at John Jay College, the City University of New York, about this and more. Edited excerpts:

Rohini Krishnamurthy: What are some of the biggest milestones in human evolution?

 

Nathan Lents: The first major milestone in the ancient past was when our ancestors began to walk upright on two legs. This happened during a relatively dry period, when the rainforest in Africa contracted, and the grassland expanded.

The apes that would become our ancestors left their life in the trees, although not completely, about four or five million years ago.

Another big milestone was the construction of simple stone tools. This began about three million years ago and was the event, more than any other that set our lineage on a new trajectory.

Instead of waiting for mutations and biological evolution, our ancestors began to navigate their ecosystems with tools rather than their bodies, which opened up new and endless possibilities, a legacy that continues to this day.

Another important event was the arrival of Homo erectus, the most successful of all our ancestors, about two million years ago. Homo erectus had a body almost indistinguishable from our own and successfully spread from Africa throughout Asia and even to the islands of the Pacific Ocean.

Our own species, Homo sapiens, arrived in the last 500,000 years. It took on our current form about 200,000 years ago.

Humans continued to develop and modernise through cultural evolution and waves of migration in and out of Africa were constant. Complex language appeared around 65,000 years ago and cities, agriculture and civilisation began in multiple places around the world between 10,000 and 15,000 years ago. The rest, as they say, is history.

RK: What may have led to the extinction of other human species? What enabled Homo sapiens to survive?

NL: There have been several human species before us and they all went extinct. In most cases, the populations were small, restricted to a limited area and we don’t know what happened.

But it seems obvious that competition with more modern humans seems certain to have played a role.

As more advanced populations encountered more primitive ones, they simply replaced them, probably not so much by direct combat or forced removal, but rather by competing for the same resources and habitat.

Steady waves of incredibly more advanced humans came out of Africa and spread all over the globe, replacing and interbreeding with the others that went before them.

Once fully modern humans arrived, it seemed the world wasn’t big enough for more than one human species.

RK: How has climate change shaped human evolution in the past and how are humans likely to evolve with climate change? 

NL: Climate changes always force species to adapt. In fact, it was a warm and dry period that nudged our species out of a shrinking rainforest and toward the open grasslands, which initiated our unique evolution.

However, the current pace of climate change is alarming because most species will not be able to adapt fast enough. Humans will use industry and technology to mitigate the damage, but without thriving ecosystems, our lifestyle is not currently sustainable.

RK: Will humans go extinct in the future?

NL: The human species is very clever and adaptable, but we have a poor sense of long-term thinking regarding the sustainable use of resources.

Human history and pre-history is filled with examples of societies that did not manage their resources wisely and suffered a collapse and catastrophic decline as a result. I hope we have learned lessons from the past, but currently, that does not appear to be the case.

No, I don’t think humans will go extinct. I think some sort of collapse is increasingly likely, but who knows how catastrophic it will be.

But, at this point, humans have spread to all corners of the globe, so it’s very hard to imagine that the entire population will disappear. We are here to stay.

RK: How will humans evolve in the future? 

NL: We are now fully in the realm of cultural evolution rather than biological evolution and this is highly unpredictable. We are beginning to take control of our biological destiny through gene editing (a technology that allows scientists to change the deoxyribonucleic acid of organisms) and other forms of human enhancement.

We will continue to solve our medical and genetic problems and hopefully move toward a future with less suffering. But it remains to be seen if we can manage and distribute our resources in a way that promotes long-term stability and harmony.

Unfortunately, I see politics and public policy as greater determinants of our future than biology. We are at a crucial point in our history.

Technology will be the primary engine of our future evolution. But this is not new. From the time the first stone tool was forged, humans have made technology to enhance or even offload the work of the body.

From clothing to fire to tools and computers, humans have used technology to expand the possibilities of what we can do and how we can live. In the very near term, humans will be curing genetic diseases and enhancing our own biology and genetics.

Brain-machine interfaces will soon allow us to reverse paralysis and replace lost limbs. We may even be able to enhance our own senses, a phenomenon that began long ago with eyeglasses and hearing aids. The future is limitless.

Subscribe to Daily Newsletter :

SUPPORT US

We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.