Early footprints re-analysed as bipedal hominin’s
It appears our early ancestors were more diverse than we thought, and co-existed with each other.
Around 3.6 million years ago in Laetoli, Northern Tanzania, a volcanic eruption spewed out ash and soot that came to settle in the plains below, thickening into a layer of mud for a few days. This would prove a boon for archaeologists millions of years later, thanks to the thousands of animal tracks found pressed into it.
Most famously, the Laetoli trackways produced the earliest evidence of bipedalism in hominins: a set of footprints discovered in the late 1970s belonging to Australopithecus
afarensis, a hominin ancestor most famously known from the fossilised specimen called Lucy.
Now, a re-analysis of different footprints, long thought to have been laid down by an upright bear, has revealed they almost definitely belonged to another bipedal hominin ancestor – albeit one with a strange and shuffling gait. This study in
cements the reality that Africa 3.6 million years ago was populated by a far more diverse range of human ancestors than once thought.
“It’s kind of odd,” says Ellison Mcnutt, corresponding author and a PHD researcher in bipedal evolution. “It didn’t quite match up with the fossils, which were admittedly few at the time; it’s an unusual set of prints that had some interesting affinities with bears.”
Mcnutt says since the original discovery of the prints in the 1970s, conventional wisdom now accepts that multiple hominins were moving across the landscape in the early days of our evolution. That’s what compelled her and the research team to reinvestigate these strange, long-forgotten prints.
By studying the mechanics of bear movement, the team realised the prints could not have ursid origins, so they went back to reexcavate at Laetoli. They noted key features of the creature’s anatomy, like the impression of the second toe, which disproved the bear theory once and for all.
But the prints were still highly unusual.
“These footprints display an example of what’s called crossstepping – it’s sort of a catwalk where one foot goes all the way in front of the other,” says Mcnutt.
“And that’s a really interesting thing, because the ability to do that and remain standing requires some adaptations to your hip and your knee that humans have, but something like a bear or a chimpanzee can’t do that.”
What is clear from the multiple sets of hominin prints at Laetoli, all laid down within hours or days, is that ancient hominins were diverse and must have not only coexisted but interacted with one another.
An Australian-led team scanning the cosmic melee for radio waves has discovered a mysterious object unlike anything astronomers have seen before. The object, GLEAM-XJ162759.5-523504, releases a giant burst of energy that crosses our line of sight and, roughly three times an hour, is one of the brightest radio sources in the sky.
“This object was appearing and disappearing over a few hours during our observations,” says team leader Natasha Hurleywalker of Curtin University.
“It was kind of spooky for an astronomer because there’s nothing known in the sky that does that.”
Unfortunately, it’s clear these signals aren’t the work of little green men. The pulses of radiation come across a wide range of frequencies, which rules out an artificial signal, pointing instead to some kind of natural process we don’t yet fully understand.
So far we know it’s a radio transient, which are radio sources that switch on and off. This has left observing astronomers stumped because there’s not enough observational data to understand what might have made the signal.
“That’s a shame,” Hurleywalker says. “They’re often going to come from very high energy processes in the universe.
“And being able to understand that would allow us to probe really extreme physics, like the intersection between quantum mechanics and general relativity.”
In this case, the team speculates this strange pattern of energy pulses is coming from a neutron star.
“What we think is that the magnetic field lines are somehow twisted and that this neutron star has undergone some kind of outburst or activity that is causing a temporary production of radio waves that makes it strong enough to produce something every 20 minutes,” Hurley-walker says.
It could also be a white dwarf, or it could be a cosmic object entirely new to science.