The skull of an ancient cave-dweller unearthed in South Africa is a million years older than previously thought, reshaping the understanding of human evolution*.
Since Australopithecus africanus fossils were discovered near Johannesburg in the Sterkfontein cave network, scientists have estimated they were under 2.6 million years old.
But advanced testing methods now suggest the most complete skull – found in 1947 and dubbed “Mrs Ples” – lived between 3.4 and 3.7 million years ago, making it possible that her species were early ancestors* of humans.
Although they walked upright and measured between 1.2m to 1.4m, the Australopithecus africanus were historically considered too young to have given rise to the homo* genus*, which includes human ancestors who lived 2.2 million years ago.
The findings, published last week in the journal Proceedings of the National Academy of Sciences, give the species about a million extra years to have evolved into the earliest humans.
It suggests the Australopithecus africanus existed at about the same time as “Lucy”, a 3.2-million-year-old cave-woman found in northern Ethiopia in 1974. Lucy belonged to the Australopithecus afarensis, long understood to be the species that most likely evolved into the earliest humans.
Scientists now say the two could have lived side-by-side and mated*, meaning our family tree is “more like a bush”, said French scientist Laurent Bruxelles, who was part of the study.
“Over a time frame of millions of years, at only 4000km away, these species had plenty of time to travel, to breed with each other,” Mr Bruxelles told AFP. “So we can largely imagine a common evolution across Africa.”
The remains are too old and brittle* for scientists to test, forcing them to analyse the surrounding sediment* instead, which formed in layers over millions of years.
Researchers said scientists previously underestimated Mrs Ples’s age because they tested mineral deposits that were more recent than the rest of the sediment around her.
This time they used a technique called “cosmogenic nuclide dating”, which measures levels of isotopes* produced when rocks were exposed to high-speed particles from outer space.
Scientists had grown sceptical* about the skull’s age because there was no sign of homo genus remains at the depth of the cave where it was found.
The Sterkfontein caves have shed light on four million years of human evolution since it was first discovered in 1936. Since then, hundreds of Australopithecus fossils have been found there, including the skeleton of Little Foot, who lived 3.67 million years ago.
“Sterkfontein has more Australopithecus fossils than anywhere else in the world,” said Purdue University Professor and lead author Darryl Granger. “But it’s hard to get a good date on them. What our data does is resolve these controversies*.”
This article was originally published by The Times and is reproduced with permission.
GLOSSARY
- evolution: theory that plants, animals and other living things originate in earlier species
- ancestors: those who came before us, what we are descended from
- homo: biological group that includes modern humans or a member of that group
- genus: class, kind, or group marked by one or more common characteristics
- mated: bred, produced young, had offspring
- brittle: being hard and rigid but without strength so prone to breaking
- sediment: rocks and minerals that have moved and settled in a new location
- isotopes: atoms with the same number of protons and electrons but different numbers of neutrons, so they have different physical properties
- sceptical: having doubts, thinking something is untrue
- controversies: theories or discussions involving very different ideas and opinions
EXTRA READING
Ancient tooth provides clue to extinct humans
Meet your two-million-year-old ‘cousin’
First look at humans’ ancient cousin
QUICK QUIZ
- How many years older than previously thought is the skull dubbed “Mrs Ples”?
- How tall did the Australopithecus africanus species measure and did they stand upright?
- How old do scientists now estimate the skull to be?
- Researchers believe the skull’s age was underestimated due to what factor?
- When were the Sterkfontein caves first discovered?
LISTEN TO THIS STORY
CLASSROOM ACTIVITIES
1. Synonym word pairs
News stories (and any piece of writing) can be boring to read if the same words are repeated many times within close proximity to one another. Therefore, good writers make use of synonyms – words that have the same or similar meanings – to vary their word choices. An example from this news article are the words “test” and “analyse”. How many other synonym word pairs can you find in the article? Write them down.
Time: allow 20 minutes to complete this activity
Curriculum Links: English
2. Extension
Write down an interesting fact that you learnt from this news story. Then, rewrite your fact a second time, swapping as many words as you can for synonyms so that the sentence retains its meaning but is quite different to the original.
Time: allow 10 minutes to complete this activity
Curriculum Links: English
VCOP ACTIVITY
Read this!
A headline on an article – or a title on your text – should capture the attention of the audience, telling them to read this now. So choosing the perfect words for a headline or title is very important.
Create three new headlines for the events that took place in this article. Remember, what you write and how you write it will set the pace for the whole text, so make sure it matches.
Read out your headlines to a partner and discuss what the article will be about based on the headline you created. Discuss the tone and mood you set in just your few, short words. Does it do the article justice? Will it capture the audience’s attention the way you hoped? Would you want to read more?
Consider how a headline or title is similar to using short, sharp sentences throughout your text. They can be just as important as complex ones. Go through the last text you wrote and highlight any short, sharp sentences that capture the audience.
