The human story: We’re still here!

The fossilised skull of a human being who died nearly two million years ago has led scientists to rethink the story of early human evolution. It’s another piece in the jigsaw puzzle of our origins.

In Fossils: The Key to the Past (2009), British palaeontologist Richard Fortey points out, “Not many years ago, there were very few named species of Homo – now there are a whole clutch of them. The original idea of ‘links in a chain’ leading to modern humankind has been replaced by a view recognising a number of branches that did not give rise to any survivors, and a rather special lineage that led to the whole panoply of the human race in all its diversity of colour, language and creed: that is to say, Homo sapiens.”

Homo sapiens is the scientific name for the human species, of which the only surviving sub-species is Homo sapiens sapiens. Homo is the human genus that includes Neanderthals and many other extinct species of hominid (the family of primates embracing chimpanzees, gorillas, orangutans, and humans). One extinct species is Homo floresiensis, nicknamed the Hobbit, and discovered in 2003 on the island of Flores in Indonesia. The remains of individuals that would have stood about 3 feet in height were found, including one complete skull.

Human-Family-TreeIn 2010 scientists announced that an entirely separate type of human co-existed and interbred with our own species around 50,000 years ago. The ancient humans were named Denisovans after the caves in Siberia where their remains were found. After sequencing a complete genome based on DNA extracted from a tooth and a finger bone, researchers concluded that there were at least four distinct types of human already in existence when anatomically modern humans (Homo sapiens sapiens) first left their African homeland.

Even more recently, anthropologists unearthed a skull at an archeological site called Dmanisi, in southern Georgia, where remains of human beings, simple stone tools and long-extinct animals have been dated to 1.8 million years old. Analysis of the skull suggests that it is a variation of Homo erectus, the first of our relatives to have body proportions like a modern human.

The odd dimensions of the fossil prompted the team to look at normal skull variations, both in modern humans and chimps, to see how they compared. They found that while the Dmanisi skulls looked different from one another, the variations were no greater than those seen among modern people and among chimps.

The discovery puts Homo erectus – the direct ancestor of Homo sapiens – on a par with other intermediaries on the human evolutionary tree: Homo rudolfensis, Homo gautengensis, Homo ergaster and possibly Homo habilis. So what? Well, it means that all these species ultimately survived and were probably outdone by a single sub-species: Homo sapiens sapiens. How and why that happened we may never know, although the ability to communicate and, therefore, to organize may have been a major factor. Up to now, we’re still here.

As American paleontologist, evolutionary biologist, and historian of science, Stephen Jay Gould wrote in “The Meaning of Life, The Big Picture” (Life Magazine, December 1988):

“The pathways that have led to our evolution are quirky, improbable, unrepeatable and utterly unpredictable. Human evolution is not random; it makes sense and can be explained after the fact. But wind back life’s tape to the dawn of time and let it play again – and you will never get humans a second time. We are here because one odd group of fishes had a peculiar fin anatomy that could transform into legs for terrestrial creatures; because the earth never froze entirely during an ice age; because a small and tenuous species, arising in Africa a quarter of a million years ago, has managed, so far, to survive by hook and by crook.”

Stephen Sondheim’s lyrics to “I’m Still Here” from his musical Follies say it all:

“Good times and bum times, I’ve seen them all
And, my dear, I’m still here
Plush velvet sometimes
Sometimes just pretzels and beer, but I’m here.”

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