July 21, 2024


ohOn November 24, 1974, the American anthropologist Donald Johanson was walking through a gorge at Hadar in the Afar region of Ethiopia with his research student, Tom Gray. The couple were looking for fossilized animal bones in the surrounding silt when Johanson spotted a small piece of arm bone – and realized that it belonged to a humanoid creature.

“We looked up the slope,” Johanson later recalled. “There lie, amazingly, a wealth of bone fragments – an almost complete lower jaw, a femur, ribs, vertebrae, and more! Tom and I screamed, hugged each other and danced like crazy any Englishman in the midday sun!

Johanson and Gray drove jubilantly back to their camp, their Land Rover horn blaring. Beer was cooled in the Awash River and roast goat was served to celebrate their discovery – which was a sensational one anyway. A total of 47 bones from a single, ancient hominin (the term used to define humans and all of our extinct bipedal relatives) were eventually uncovered at the site by Johanson and Gray.

A sculptor’s rendering of the hominin Australopithecus afarensis. Photo: Dave Einsel/Getty Images

The fragments they collected amounted to about 40% of a complete skeleton, and subsequent dating showed these remains to be about 3.2 m years old. At the time, it was the oldest humanoid creature ever unearthed by fossil hunters, and she was given the name Lucy.

Fifty years later, Johanson and Gray’s discovery remains one of the most significant breakthroughs ever made in the field of human paleontology. From the pelvis, scientists concluded that it belonged to a female, while her short legs suggested she was only about four feet tall. This discovery was followed up with other, similar finds, some in Ethiopia and some in Tanzania, and in 1978 Johanson – along with a colleague, Tim White – announced that these bones, including Lucy’s, all belonged to a single, previously unknown hominin species they named Australopithecus afarensis: the Southern Monkey from Far.

Johanson and White placed afarensis at the base of a tree of ancestors that led to more recent species, such as Homo erectus and later the Neanderthals and Homo sapiens. From this perspective, Lucy was the mother of mankind.

And while subsequent research and other fossil finds have led to some revisions to Lucy’s elevated status, the fact that she walked upright despite her small brain was – on its own – a discovery of considerable importance, says paleoanthropologist Chris Stringer of the Natural History Museum, London.

“Humans have three key characteristics: our ability to walk upright, our ability to make tools and our big brains,” says Stringer. “But a crucial question is: which of these features arrived first in our evolution? What was the first step that led our ancestors down a path that eventually led to the appearance of Homo sapiens?”

In The Descent of Man, Darwin argued that the three human characteristics – bipedality, tool-making and large brains – evolved together, a development in one stimulating the other to evolve further. Based on that, brain augmentation would be part of human evolution from its inception. Then came the discovery of Lucy.

“Lucy has shown that this idea is simply not true,” says Stringer. “Her skeleton showed that our ancestors walked on two feet long before their brains got big.”

This point is supported by Zeresenay Alemseged, a paleoanthropologist at the University of Chicago. “Lucy showed that a big brain is not the sine qua non of being a member of the human race,” he says.

Donald Johanson (left) assembles the Lucy skeleton for the first time with French colleague Maurice Taieb. Photo: Human Origins, Arizona State University

It’s an intriguing observation, one that raises key questions. Why did our ancestors adopt a bipedal gait in the first place? What evolutionary advantages did they gain from standing on two feet?

Many answers have been proposed over the years. If they walked on two feet, ape-men would have had arms free to pick fruit from low-lying branches and could also carry food and babies. Standing upright would have made them appear larger and more intimidating, while reducing the level of harsh African sunlight hitting their backs.

These are all tantalizing suggestions, although the most likely reason was more prosaic, argues Alemseged. “When you walk on two legs, as opposed to four, you save energy. It is as simple as that. You use fewer calories – and remember, our early ancestors didn’t struggle to lose weight like we do today. They had to get all the energy they could get and exploit it with maximum efficiency. Walking on two feet helped them do that.”

People today pay for that transition to an upright gait – in terms of back pain and other skeletal problems that arise in later life. On the other hand, we reaped the benefits in terms of expanding our brains that eventually followed in the wake of our acceptance of bipedalism.

Lucy’s discovery posted afarensis at the heart of the story of human evolution. However, since her presence was first revealed in Hadar, many fossils of other, even older hominin species have been found. This includes Australopithecus anamensiswhich – four million years ago – walked over terrain that today lies in Kenya and Ethiopia, and Ardipithecus ramidus, who lived in a similar part of Africa about 4.5 million years ago. Importantly, these early apes also have anatomies that suggest they were bipedal.

So, one of these species – and not afarensis – could have been the true origin of the lineage that led to Homo sapiens? Lucy’s family could simply have been a branch of that family tree, and not a direct link to modern humans. In other words, was Lucy merely a great aunt of mankind, not his mother? Some scientists believe that this may be the case. However, Alemseged has his doubts.

“These earlier hominins probably walked upright for part of the time, but many probably lived in trees for most of their lives. In contrast, Lucy and her afarensis family spent a lot of time walking upright. They were decisive in the transformation of our genus into one committed to an upright posture.”

With Lucy, our generation has reached the stage where walking upright has become commonplace. We became obligate bipeds, the defining feature of the genus that eventually spawned Homo sapiens.

Alemseged’s own contribution to this field was his discovery, on 10 December 2000, of Selam, the almost complete fossil skull and parts of the skeleton of a child of Australopithecus afarensis. It is sometimes referred to as “Dikika child” or “Lucy’s child”, although this latter attribution is a misnomer, as the skull has been dated as 3.3 million years old and is therefore more than 100,000 years older than Lucy .

“We have now found afarensis in Tanzania, Chad, Kenya and Ethiopia, and we know that Lucy and her family must have lived in these parts of Africa for nearly a million years,” adds Alemseged. “That antiquity and extensive geographic distribution convinces me that it is the most likely candidate to have given rise to the many species of the Homo genus and ultimately to our own species, Homo sapiens.”

Lucy’s remains are now housed at the National Museum of Ethiopia in Addis Ababa, where Alemseged – who was born in Ethiopia – made headlines in 2015 when he was on hand. to show Lucy to Barack Obama during the president’s state visit. She is the forerunner of all people today, he told Obama. “Every single person, even Donald Trump.”

Lucy’s skull reconstructed. Photo: Sabena Jane Blackbird/Alamy

Other scientists are more cautious about Lucy’s exact relationship to humans today. “The problem is that we only have two areas from which we have good fossil evidence of hominin evolution: in the Rift Valley areas of Kenya, Tanzania and Ethiopia; and in South Africa,” Stringer points out.

“In the former there are lakes, rivers and sediments in which it is relatively easy to find fossils, while in South Africa there are many caves where early hominins fossilized. This gives you a very biased picture of hominin evolution in Africa. We don’t know what happened elsewhere on the continent,” adds Stringer. “It’s a bit like the drunk man who looks for keys he dropped at night and only looks where there are street lights – because those are the only places he can see. Currently there is a shortage of places to find [fossil remains in Africa] and from places where people actually looked, and that limits the evidence we can gather about exactly how the human lineage evolved millions of years ago.”

Nevertheless, it is clear that Lucy could play a major role in the development of our understanding of our own species – even if her naming was rather haphazard, as Johanson admitted in reminiscing about the tumultuous days that followed her discovery in Hadar. “Such a noble little fossil lady surely deserved a name, we all thought, and as we sat listening to Beatles songs one night, someone said, ‘Why don’t we name her after Lucy?’ You know, after Lucy in the Sky With Diamonds.’ That’s how she became Lucy.”

However, it could easily have been a completely different name, as Caitlin Schrein has pointed out in Earth. The Beatles song was recorded seven years earlier. And if Johanson and his colleagues were more up-to-date with their choice of pop music, or had a better availability of records, they would probably have played more contemporary tracks. Songs may even have included some of the hits of 1974 – such as Annie’s Song by John Denver or Bennie and the Jets by Elton John. If they had listened to these tracks, the world’s most famous fossil skeleton might have had a different name.

However, the name is perhaps irrelevant. “The crucial point is that she was a great pioneer in highlighting early human evolution,” says Stringer.



Source link

Leave a Reply

Your email address will not be published. Required fields are marked *