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Sunday, 15 March 2015

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Evolution’s missing link

'Where we are going as a species is a big question. Human evolution certainly hasn't stopped. Every time individuals produce a new zygote, there's a reshuffling and recombination of genes. And we don't know where all of that is going to take us.' That quote from Donald Carl Johanson, the American paleoanthropologist who discovered the fossil of a female hominid australopithecine known as “Lucy” in Hadar, Ethiopia, reminds us that human evolution is a story that is yet to be finished. In fact, we do not even know how it started in the first place and how humans began to dominate our planet.

Humans are easily the most dominant species on the planet today, but exactly when did they begin their domination? Was it 50,000 years ago? Was it 10,000 years ago or was it 5,000? Latest research indicates that we have been really dominating the earth for much less than that.

Anthropocene

A new study published in the science journal Nature has indicated that the human-dominated geological epoch known as the Anthropocene probably began around the year 1610, which is really much closer to the present period than most of us thought. The study conducted by University College London (UCL) showed that previous epochs began and ended due to factors including meteorite strikes, sustained volcanic eruptions and the shifting of the continents.

The study authors systematically compared the major environmental impacts of human activity over the past 50,000 years against these two formal requirements. Just two dates met the criteria i.e.1610, when the collision of the New and Old Worlds a century earlier was first felt globally; and 1964, associated with the fallout from nuclear weapons tests. The researchers conclude that 1610 is the stronger candidate.

What exactly makes 1610 really special? The scientists say the 1492 arrival of Europeans in the Americas and subsequent global trade moved species to new continents and oceans, resulting in a global re-ordering of life on Earth and this rapid, repeated, cross-ocean exchange of species is without precedent in Earth's history. The Anthropocene probably began when species jumped continents, starting when the Old World met the New. Colonisation of the New World led to the deaths of about 50 million indigenous people, most within a few decades of the 16th century due to smallpox.

Revolution

The process was accelerated when the Industrial Revolution began in 18th century. It was a clear turning point in human history, and the rise of atmospheric carbon dioxide from fossil fuel use is a long-term global environmental change of critical importance. It is a problem that affects us to this day and although efforts are being made to reduce CO2 emissions and greenhouse gases, it will probably take a couple of centuries to undo the damage already caused and stop this process altogether.

There is a well-known example where the whole history of Planet Earth is condensed to just one hour and the rise of humans occupies just the last 30 seconds or less. This shows that mankind’s reign on Planet Earth is very short, cosmically speaking. However, there are several unsolved mysteries in terms of human evolution which are being probed only now.

In fact, the recent discovery of a 2.8-million-year-old partial jawbone in Africa could rewrite the history of human evolution. The fossil record for humans between two million and three million years ago is just very poor and has long been known as a gap in human evolution. An international team of researchers found the lower jawbone, complete with teeth, at the Ledi-Geraru site in the Ethiopian Rift Valley. This find could apparently fill a gap in the fossil record that has frustrated scientists.

Discovery

The discovery of this yet-to-be named hominid pushes back the appearance of the Homo genus by some 400,000 years. This fossil strongly indicates that Homo - the genus to which we belong - first emerged in East Africa approximately three-million years ago when a select group of hominids transitioned away from the more ape-like Australopithecus. Fossils of this nature are exceptionally rare. Specimens from this particular time period, between 2.5- and 3-million years ago, are few and far between and those that are found are typically not very well preserved.

The teeth found in this perfectly preserved jawbone, now called the “perfect missing link” suggest a change in diet from the mainly fruit-eating Australopithecus towards a more meat-based diet that would also have required the use of tools. What this suggests is that three million years ago, there would have been a very ape-like creature with long arms, living in the forest, probably eating fruit. Two million years ago Homo would have arrived with the tools, a large brain and shorter arms.

There is a debate whether two ‘human-like’ species would have lived together at the same time during one epoch, but the humanoid with the bigger brains and the ability to use tools would have won the race to domination. Over a period of time, man mastered the art (and science) of agriculture, animal domestication and a sedentary lifestyle, a departure from the hunter-gatherer lifestyle of the more primitive times.

Usefulness

Human evolution is a fascinating field of study. Some may question the usefulness of dwelling upon our collective past at considerable expense (these research efforts are incredibly expensive and time consuming), mainly because nothing can seemingly be gained by understanding our past. But this is not true at all.

It is only by studying our past that we can take stock of where we are - and where we are heading. Understanding how humans have contributed to change the Earth (via such examples as 1610) will help us save it from further peril in the future. Reconstructing the evolutionary patterns through millions of years will also tell us how we could evolve in the future. In fact, future evolution is a hot subject, with various studies predicting that Man will essentially have a much changed body and facial structure just 100,000 years down the line. This studying our past, our history, is very important in more ways than one to map our future.

 

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