Hello, This is a tooth (although it doesn’t look like one).
which at one time, about 27000 years ago, belonged in the mouth of a Panamerican ground sloth much like this one:
It’s just one tooth, but it tells us about the sloth. Imagine your own teeth one day, some 27,000 or more years from now when homo sapiens has gone extinct, and your teeth are found and are in the hands of a scientist of the time, whoever or whatever that person or robot might be, and who will have replaced us as the highest form of life on earth.
What would our teeth tell “him” about how we lived when it was our turn to be living on the earth? Not being a dentist, nor a paleontologist, nor not knowing anything at all about the time 27,000 years from now when our teeth may be found by a paleontologist, I have no idea.
Now the fabulous ground sloths are no more with us, all gone extinct. The North American Eremotherium laurillardi – the six-metre-long animal in the picture occupied a range that stretched from the southern states of the US to Brazil,
but did not survive the advent of homo sapiens about 11.000 years ago.
But let me get back to the single tooth and what it tells us. It’s kind of unbelievable what we can learn from a sloth’s tooth, at least just so far if we know how and where to look, about the life secrets of a single animal.
I take what follows from a report by Dyani Lewis in the internet news letter COSMOS taken in turn from the Journal Science Advances of February 28 of this year:
But why am I writing about the giant sloth? Well I’ve just been watching Michael Cohen being brutally and unfairly attacked by the Republican members of the House Intelligence Committee, and I desperately wanted to walk away and immerse myself in something real. The work of scientists is real, the work of the representatives in Washington DC is not. Our president has not yet understood this, about Washington and about science.
But here is a little of what the scientists have learned about this fabulous (and lazy?) animal who did survive the last Ice Age. Will we survive the present age of the Great Warming?
Analysis of the tooth, prised from a clay ledge metres below the surface of a water-filled sink-hole in central Belize, reveals details about what the sloth ate, and the climate it lived in.
Jean Larmon from the University of Illinois at Urbana-Champaign, US, and colleagues measured the amounts of specific chemical elements that were incorporated into the tooth when the sloth was alive.
The isotopes carbon-13 and oxygen-18 are particularly useful. Carbon-13 values can tell scientists about the types of food the sloth consumed, and oxygen-18 levels reveal the aridity of the climate at the time.
Because amounts of these isotopes slowly change, or decay, over time, they can also reveal the age of any object containing them….In other animals, the hard outer coating of teeth – the enamel – is usually used in stable isotope analysis. But sloth teeth grow continuously – much like a rat’s incisors – and therefore lack it.
Larmon and colleagues instead took readings from different layers of the sloth tooth. The values varied. Using a technique that measures the amount of light emitted by a fossil, they ascertained that the most reliable values were from a hard layer called orthodentin. By sampling along the length of this layer the team built up a picture of the sloth’s life over a period of about a year.
The animal lived smack in the middle of the last glacial maximum, the most recent time during the Last Glacial Period when ice sheets were at their greatest extent, well before humans arrived in the Americas. At the time, Central America wasn’t covered in tropical forests as it is today. The region was much drier, covered in savannah and juniper scrub vegetation.
The sloth experienced two brief wet seasons, separated by a long dry season. Its diet changed with the seasons, suggesting it was an opportunistic feeder. This could have held it in good stead for adapting to the increasingly arid conditions of the period. During the wet seasons, it most likely ate grasses and shrubs, but no leafy trees.
To understand the biology and the ecology of these animals when they were alive is absolutely critical. Armed with that information, scientists are better able to assess what factors – a changing climate, say, or the arrival of humans – eventually led to the species’ extinction.
But the reasons for the demise of large animals, collectively known as megafauna, is an enduring mystery. And while this present study describes details of just one individual’s life, it contributes to a greater understanding of the prehistoric environment. Dyani Lewis