Last week’s task was to summarize in a few hundred words the evolution of humans which began six to seven million years ago and continues to the present.

The path began with a variety of small ape-like species, which became increasingly bipedal over four to five million years before transitioning to increasingly larger brained, fully bipedal species variants, some of which, like homo erectus, migrated throughout Eurasia including Britain as well as within Africa.

The story wrapped up with our two cousin species, the denisovans in Asia and neanderthals in Europe before anatomically and possibly behaviorally modern humans appeared in what is now Morocco as early as 300,000 years ago. 

Along the evolutionary path, there were many transitional species, some side show species such as homo floresiensis, homo luzonensis and homo naledi, and periods when two or more variants lived at the same time and even region, if not quite the same habitat, until in the last 30,000 years, when one species remained — us.

Adding to the number of species variants are those known only by the DNA they left behind and others yet to discovered or lost forever. 

The evolutionary path to modern humans was never a certainty. For example, there have been near-extinction events such as the eruption of Mount Toba in Indonesia 70,000 years ago, and far worse, nearly a million years ago, when the total population of prehumans plummeted from almost one million to less than 3,000 in the face of prolonged harsh climate and so remained for the following 100,000 years before recovering. 

Even so, prior to humans settling down 10,000 years ago, estimates of the world-wide population of modern humans world are small — somewhere between one and 10 million total scattered in small groups.

The latter made them more vulnerable in the face of sustained severe weather, lack of food and as was the case for the neanderthals, led to their extinction because of inbreeding and the accompanying accumulation of harmful genetic variants as happened to other species such as woolly mammoths.  

From the beginning, the path to modern humans was never scripted because of the important role natural selection and chance play in the evolution of most species including our own, and the corollary that any rerun of hominin evolution would most unlikely come up with a species quite like our own.

Of course, as much as evolution might not come up with a species as clever as us, there’s always the possibility that another run at evolution might have come up with species far more clever and hopefully wiser than ours.

Which brings me to this question — what does the future hold for our species?

Predicting the future for our species is dicey given current world politics, economics and climate change, but predicting the far future is more certain.

For example, glacial and interglacial periods will continue to cycle every 100,000 years much as they have for the last several few million years, because the cycle is dictated by cyclic changes in the orbit of the earth about the sun. 

On a much longer scale, in three to four billion years, our sun will likely have run through enough of its hydrogen and gravitational force to expand and engulf Earth and possibly even Mars, roasting both and killing off all life on Earth.

How do we know that? From observation of similar fates for similar sized stars and extrapolating to what’s likely to happen with our sun.

But what about our species? What’s our future? If the past is prologue to the future, we are likely to continue to evolve, indeed, as genetic studies suggest.

But so far there’s little, if any, evidence that human intelligence has changed within the last several thousand years or that there have been noticeable changes in physique except for whatever improvements have taken place through better health.

The collective fossil evidence suggests that for much our history few lived much beyond their 30s; such were the risks of predators, hunting large dangerous animals, unpredictable food sources, and clashes within and between bands. 

Whether we evolve into another species as many of our predecessor species did is hard to predict. The evolution of a menagerie of hominin variants to humans took several million years and was based on genetic changes in far fewer humans than the eight million and counting humans living now. 

Based on those numbers, there should be many more mutational changes in the modern human genome than in the past and, given that mixing of humans has become common, those changes stand a much better chance of becoming widely incorporated in the human genome raising the possibility of budding future species not in several hundred years, but much earlier.

What’s coming is editing our genome to enhance desired cognitive, physical and health-enhancing genes. The tools exist now for editing a few genes, but editing the many related genes necessary to enhance specific traits is several decades away.

When that time comes, humans with the financial resources and connections may seek advantages for themselves and their children through modifying their own genes and those of their children. 

What a frightening prospect.

Dr. William Brown is a professor of neurology at McMaster University and co-founder of the InfoHealth series at the Niagara-on-the-Lake Public Library.