The 3.6 million-year-old footprints that reveal how our ancient male ancestors had more than one mate at a time

  • 13 footprints belonging to five Australopithecus afarensis were found
  • A male is thought to have walked at least 30 metres with four females
  • Calculations of height suggest he was at least 20cm taller than the females
  • The prints suggest Australopithecus afarensis may have had a gorilla-like social arrangement with a dominant male who mated with several women
Footprints belonging to a group of early humans who lived 3.6 million years ago have been uncovered in Tanzania.
The early impressions were made when five of our ancient relatives - most likely Australopithecus afarensis - walked across wet volcanic ash.
Researchers say the footprints suggest that members of Australopithecus afarensis may have had a gorilla-like social arrangement of one dominant male mating with several females. 
Footprints belonging to a group of early humans who lived millions of years ago have been uncovered in Tanzania. A man, accompanied by four women was thought to have walked at least 30 metres over the volcanic ash that later hardened into rock
Footprints belonging to a group of early humans who lived millions of years ago have been uncovered in Tanzania. A man, accompanied by four women was thought to have walked at least 30 metres over the volcanic ash that later hardened into rock

AUSTRALOPITHECUS AFARENSIS 

Australopithecus afarensis is one of the longest-lived and best-known early human species, who lived 3.85 to 2.95 million years ago in Eastern Africa.
The species survived for more than 900,000 years, which is over four times as long as our own species has been around.
Similar to chimpanzees, Au. afarensis children grew rapidly after birth and reached adulthood earlier than modern humans. 
Au. afarensis had both ape and human characteristics, with apelike face proportions and long, strong arms with curved fingers adapted for climbing trees.
They also had small canine teeth like all other early humans, and a body that stood on two legs and regularly walked upright.
The 13 footprints were discovered in Laetoli, Tanzania, by an international group of researchers, led by Sapienza University in Rome.
The researchers believe that they belong to five members of Australopithecus afarensis – the prehuman species best known for the fossil skeleton, nicknamed 'Lucy.'
A man, accompanied by four women was thought to have walked at least 30 metres over the volcanic ash that later hardened into rock.
Professor Giorgio Manzi, lead author of the study, said: 'This novel evidence, taken as a whole with the previous findings, portrays several early hominins moving as a group through the landscape following a volcanic eruption and subsequent rainfall. But there is more.
'The footprints of one of the new individuals are astonishingly larger than anyone else's in the group, suggesting that he was a large male member of the species.
The researchers believe that they belong to five members of Australopithecus afarensis – the prehuman species best known for the fossil skeleton, nicknamed 'Lucy'
The researchers believe that they belong to five members of Australopithecus afarensis – the prehuman species best known for the fossil skeleton, nicknamed 'Lucy'
'In fact, the 165cm stature indicated by his footprints makes him the largest Australopithecus specimen identified to date.'
The findings differ from previous studies that have suggested that Australopithecus afarensis males only had one sexual partner.
A study in 2003 by researchers from Penn State University performed extensive simulations using modern humans, chimpanzees, and gorillas to understand the sex lives of Australopithecus afarensis individuals.
In their paper, the researchers, led by Dr Philip Reno, wrote that 'the reproductive strategy of A afarensis was principally monogamy.'
The prints were found at Laetoli – a site which is famous for another set of smaller footprints left by Australopithecus afarensis individuals.
In the 1970s, those prints made headlines as the earliest clear evidence of upright walking by our ancestors.
This illustration provided by Dawid A. Iurino in December 2016 shows a reconstruction of the northern Tanzanian Laetoli site 3.66 million years ago, where the footprints were found
This illustration provided by Dawid A. Iurino in December 2016 shows a reconstruction of the northern Tanzanian Laetoli site 3.66 million years ago, where the footprints were found

ESTIMATING HEIGHT FROM FOOTPRINTS 

Measurements of the length and width of the footprints, stride length and the angle of the gait allowed the researchers to calculate rough weights and heights for the five. 
The male came in at the heaviest and tallest, weighing 48.1kg (100 pounds) and measuring about 5 foot 5 (165 centimetres), while the lightest only weighed 28.5kg.
If these measurements are correct, this would mean the male loomed more than 20 centimetres (eight inches) above his fellow walkers.
The newly found prints are only 150 metres away.
Measurements of the length and width of the footprints, stride length and the angle of the gait allowed the researchers to calculate rough weights and heights for the five.
The male came in at the heaviest and tallest, weighing 48.1kg (100lbs) and measuring about 5 foot 5 (165cm), while the lightest only weighed 28.5kg.
If these measurements are correct, this would mean the male loomed more than 20 centimetres (eight inches) above his fellow walkers.
Dr Marco Cherin, who also worked on the study, said: 'A tentative conclusion is that the group consisted of one male, two or three females, and one or two juveniles, which leads us to believe that the male - and therefore other males in the species - had more than one female mate.'
Measurements of the length and width of the footprints, stride length and the angle of the gait allowed the researchers to calculate rough weights and heights for the five
Measurements of the length and width of the footprints, stride length and the angle of the gait allowed the researchers to calculate rough weights and heights for the five
The large male-female disparity suggests that Australopithecus afarensis may have had a gorilla-like social arrangement of one dominant male, with a group of females and their offspring. 
But not everyone is convinced by the researchers' analysis of the height.
Dr William Jungers, a research associate at the Association Vahatra in Madagascar who wrote a commentary on the study, says the estimate is suspect.
The prints were found at Laetoli – a site which is famous for another set of smaller footprints left by Australopithecus afarensis individuals
The prints were found at Laetoli – a site which is famous for another set of smaller footprints left by Australopithecus afarensis individuals
In his commentary, Dr Jungers wrote: 'It is important to note that foot length has only been roughly estimated for this ancient species, and that the height estimates would change if a different foot length-to-stature ratio was used.' 
In November, researchers analysed the fossilised arm bones of Lucy, an early hominin from the Australopithecus afarensis species, and suggested that she was a tree climber.
Scans of Lucy's arm bones revealed her upper limbs were somewhere between a modern human and a chimpanzee.
Scans of Lucy's arm bones revealed her upper limbs were somewhere between a modern human and a chimpanzee
The evidence gleaned from the scans proves Lucy spent time climbing and used her arms to pull herself up, potentially ending the long-running debate among palaeontologists
In November, researchers analysed the fossilised arm bones of Lucy, an early hominin from the Australopithecus afarensis species, and suggested that she was a tree climber
The evidence gleaned from the scans proves she spent time climbing and used her arms to pull herself up, potentially ending the long-running debate among palaeontologists.
It also expands on evidence from earlier this year which claimed that Lucy may have died from a fall, most likely from a tree.
Taken together, the evidence suggests that Australopithecus afarensis may have been spent time on the ground, returning to the safety of the trees for food and to sleep, to avoid predators. 
 The 13 footprints were discovered in Laetoli, Tanzania, by an international group of researchers, led by Sapienza University in Rome
 The 13 footprints were discovered in Laetoli, Tanzania, by an international group of researchers, led by Sapienza University in Rome