LIFE SCIENCES – Hobbit mystery deepens
It’s closest relative is a 1.75 million year old African. ELIZABETH FINKEL reports.
The metre-tall Homo floresiensis, popularly known as the hobbit, just keeps upending the history of human evolution. The latest chapter, published in the Journal of Human Evolution in April, concludes that it’s closest relative was Homo habilis who lived 9000 kilometres away in Ethiopia. Not only has this left archaeologists scratching their heads, it challenges the textbook view that Homo erectus was the first ancient human species to leave Africa.
It was 2003 when Mike Morwood and colleagues first reported the discovery of the papery bones of H. Floresiensis alongside stone tools in the sediments of the vast Liang Bua cave in Flores. To Morwood the bones resembled those of Ethiopia’s famous 3.2 million-year old Australopithecine, Lucy.
How could such a primitive hominin species have reached Flores? And how could they have endured till 18,000 years ago? That was the initial date reported for the remains. Rather than accept these mind-boggling propositions, some anthropologists argued the hobbit was not ancient but a diseased modern human, perhaps afflicted by dwarfism.
The suggestion was that H. erectus arrived on the island and shrank – just like the Asian elephant that shrank to become Flores’ dwarf stegodon.
That debate has largely gone away – aided by new dating techniques indicating the hobbits were a very enduring bunch: tool remains show they occupied the cave from 190,000 to 50,000 years ago.
The new debate lies with the hobbit’s ancestors. Two recent studies concluded that H. erectus was the closest relative. That made sense: H. erectus skulls had, after all, been found in nearby Java, though not on Flores itself.
But a new analysis led by Debbie Argue’s team at the Australian National University pushes the pendulum back closer to Lucy. While previous analyses employed only skulls and teeth, the current study included 133 data points ranging across the skull, jaws, teeth, arms, legs and shoulders. The verdict? As far as descent from Homo erectus, “All the tests say it doesn’t fit,” Argue says.
The inside of the floresiensis lower jaw was particularly telling. It showed pronounced reinforcing mounds known as the superior and inferior tranverse torus, never found in modern humans, and only in a very muted form in Homo erectus. Furthermore the hobbits had oversized arms and feet like chimps – “body proportions much more like Homo habilis or Australopethicus than Homo erectus,” explains Argue.
The latest analysis places the hobbit as most likely a sister species to H. habilis, which lived in Africa about 1.75 million years ago.
How, then, did such a primitive hominin get to Flores from Africa – a journey across water – more than 190,000 years ago? And if a relative of habilis did make it out of Africa, how come no other remains have been found along the way?
One way out of the quandary is to suggest that H. erectus arrived on the island and reverted to a primitive form. Argue finds this implausible: “Why would the jaw of Homo erectus evolve back to the primitive condition?”
Ultimately it’s a case of more questions than answers.
Scientists have observed one of the most powerful astronomical events ever seen — the collision of two giant black holes to form an even larger black hole.
It’s the third time since 2015 that such a collision has been observed by an instrument in the US called the Laser Interferometer Gravitational-wave Observatory (LIGO), which consists of a pair of detectors, one in Hanford, Washington, and the other in Livingston, Louisiana, each designed to measure gravitational waves from distant cosmological events.
Gravitational waves are ripples in the fabric of space, created by movements of massive objects.
“Normally we don’t think of space as having any properties at all, so it’s counterintuitive,” says Michael Landry, director of LIGO’S Hanford observatory.
Nevertheless, he says, Einstein’s theory of general relativity predicts that space can expand, contract or vibrate, thereby distorting the medium in which we all live.
These waves can be measured, he adds, because the distortions they produce look like changes in the length of any object they pass through.
Landry compares it to stretching the canvas of a painting: “If I stretch the medium, the painting gets distorted.”
In the latest case, LIGO saw the rapidly vibrating distortions produced as the two black holes spiralled toward each other before merging. The energy thus released in the form of gravitational waves was the equivalent of two Sun-sized stars being dematerialised in one-third of a second.
Once the collision was complete, the new black hole had a mass about 50 times that of the Sun.
It’s an important find because it suggests that black holes of this size may be fairly common.
“Before our discoveries we didn’t even know for sure that these black holes existed,” says Laura Cadonati of Georgia Tech University. “We know now they do. They may have played an important role in the early universe.”
The new finding allowed researchers to calculate whether the colliding black holes were spinning in the same direction as they circled each other before the collision.
“Imagine two tornadoes rotating each other,” says Laura Cadonati of Georgia Tech University. “They could be [in] the same as the orbit, or opposed, or at any angle in between.”
Computer modelling showed that the signals detected by LIGO contained the “gravitational fingerprints” of black holes with spins that did not align with their orbit.
Cadonati says: “This favours the theory that these two black holes formed separately then paired up, rather than being formed from the collapse of two already paired stars.”
The research was published in the journal Physical Review Letters.