Tag Archives: archaeology

Never say die

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Reading Remnants of Ancient Life by Dale Greenwalt for New Scientist, 11 January 2023

What is a fossil made of? Mineralised rocky fossils are what spring to mind at a first mention of the word, but the preserved fauna of the burgess shale are pure carbon, a kind of proto-coal. Then there are those tantalising cretaceous insects preserved in amber.

Whatever they are made of, fossils contain treasures. The first really good microscopic study of (mineralised) dinosaur bone, revealing its internal structure, was written up in 1850 by the British palaeontologist Gideon Mantell.

Still, classifying fossil organisms on the basis of their shape and their location seemed to be virtually the only weapon in the paleobiologist’s arsenal — until 1993. That was the year Michael Crichton’s novel Jurassic Park famously captured the excitement of a field in turmoil, as ancient pigments, proteins, and DNA were being detected (not too reliably at first) in all manner of fossil substrates, including rock.

Jurassic Park’s blood-sucking insects fossilised in amber were a bust. Though seemingly perfectly preserved on the outside, they turned out to be hollow.

Mind you, the author of Remnants (a dull title for this vivid and gripping book) has himself has managed to get traces of ancient haemoglobin out of the bloated stomach of a fossilised mosquito — so never say die.

Greenwalt, who spends eleven months of every year “buried deep in the bowels of the Smithsonian’s National Museum of Natural History in Washington, DC,” has brought to the surface a riveting account of a field achieving insights quite as revolutionary as any conjectured by Crichton. The finds are extraordinary enough: a cholesterol-like molecule in a 380-million-year-old crustacean; chitin from the exoskeleton of a fossil from the 505-million-year-old burgess shale. Even more extraordinary are the inferences we can then draw about the physiology, behaviour, and evolution of these extinct organisms. Even from traces that are smeared, fragmented, degraded, and condensed, even from cyclized and polymerized materials, valuable insights can be drawn. It is even possible to calculate and construct putative “ancestral proteins” and from their study, conclude that Earth’s life had its origins at the mouths of deep ocean vents!

The story of biomolecules in palaeontology has its salutary side. A generation of brilliant innovators have had to calm down, learn the limitations of their new techniques, and return, as often as not, to the insights of comparative anatomy to confirm and calibrate their work. Polymerase-chain-reaction sequencing (PCR) is the engine powering our ever older and ever more complete ancient DNA sequences, but early teething problems included publication of a DNA sequence thought to be from a 120-million-year-old weevil that actually belonged to a fungus. Technologies prove their worth over time.

More problematic are the cul-de-sacs. In 2007 Greenwalt’s colleague, the palaeontologist Mary Schweitzer reported her lab had recovered short sequences of collagen from the femur of a 68-million-year-old Tyrannosaurus rex. As Matthew Collins at the University of Copenhagen complains, “It’s great work. I just can’t replicate it.” Schweitzer’s methodology has survived 15 years’ hard interrogation, it may simply be that animal proteins cannot survive more than about 4 million years. That still makes them much hardier than plant proteins, which only last for about 30,000 years.

Against these fascinating controversies and surprising dead-ends Greenwalt sets many wonders, not least “the seemingly unlimited potential of ancient DNA to shed light on the ancestry of our species, Homo sapiens”. And for short-changed botanists, there’s an extraordinary twist in Greenwalt’s tale whereby it may become possible to classify plants based, not on their morphology or even their DNA, but on the repertoire of small biomolecules they leave behind. “The biomolecular components of plants have been found as biomarkers in rocks that are two and a half billion — with a ‘b’!—years old,” Greenwalt exclaims (p204). The 3.7-billion-year-old cyano-bacteria that produced stromatolites in Greenland are the same age as the rocks at Mars’s Gale Crater: “Are authentic ancient biomolecules on Mars so implausible?” Greenwalt asks.

His day job may keep him for months at a time in the Smithsonian’s basement, but Greenwalt’s gaze is set firmly on the stars.

“The idea that life is absurd bothers him”

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Reading Life As Told by a Sapiens to a Neanderthal by Juan José Millás and Juan Luis Arsuaga for the Telegraph, 27 July 2022

In 2013 the oldest known human DNA was discovered, in a complex of caves in the Sierra de Atapuerca in northern Spain. It belongs to an early hominid, Homo heidelbergensis, who lived 400,000 years ago, and to whom we owe the invention of the fireplace.

Arsuaga has built an illustrious career around excavations in Atapuerca, a site humans have occupied continuously for a million years, from the dawn of Homo sapiens to the bronze age. He knows a lot about how humans evolved, and he is an eloquent communicator. “As he talked,” the novelist Juan José Millás recalls, “I realised what a great sense of the theatrical Arsuaga had. He was a master of oral storytelling. He knew when he had his audience, and when he was running the risk of losing them. He endeared himself by combining intellectual precision with a kind of helplessness.”

It’s Aruaga’s eloquence that first persuaded Millás that the two of them should collaborate on a book — a Boswellian confection in which Millás (humble, curious, a klutz, and frequently brow-beaten) follows Arsuaga around with a dictaphone capturing the great man’s observations. “In Spain,” he remarks, early on, “there are two principal periods: the first runs from the Neolithic to 1958, at which point the social planning by the Opus Dei technocrats comes in. Until then, the countryside was a place full of people, full of voices, life here was not a sad thing, there were children running around. It would be like walking down the street. By 1970, the countryside was empty, there was nobody left.”

Millás casts Arsuaga as the representative of Homo sapiens: articulate, eclectic, self-aware and tragical. Millás casts himself as Homo neanderthalis, not quite as quick on the uptake as his more successful cousin. Neanderthals are a species not exactly lost to history (Sapiens and Neanderthals interbred, after all) but no longer active in it, either.

The idea is that Arsuaga the high-brow leads our beetle-browed narrator hither and thither across northern Spain, on foot or in his trusty Nissan Juke, up lost valleys (to understand the evolution of hunting) and through deserted playgrounds (to grasp the mechanics of bipedalism), past market stalls (to grasp the historical significance of diet) and into a sex shop (to discuss the relative size of primate testicles) and building, bit by bit, a dazzling picture of the continuities that exist between our ancient and contemporary selves.

For many, the devil will be in the detail. Take, for example, Millás’s Neanderthals. He is not exactly wrong in what he says about them, but he is writing, in the most general and allusive terms, into a field that is developing frighteningly fast. It‘s hard, then, for us to know how literally to take the author’s showier gestures. Millás says, about that famous interbreeding, that “The Sapiens, being the smart ones, did it out of vice, while the Neanderthals, who were more naïve, did it out of love.” With Neanderthal intelligence and sociality a topic of so much fierce debate, such statements as this may be met with more scepticism than appreciation.

This is as much a buddy story as it is a virtuosic work of popular science. In unpacking our evolutionary past, Millas also brings his human subject to light. Arsuaga holds to the tragic view of life espoused by the fin de siecle Spanish essayist Miguel de Unamuno. Millás, a more common-or-garden depressive, finds Arsuaga’s combination of high spirits and annoyance hard to read. Deposited on the outskirts of Madrid, and half suspecting he’s been actually thrown out of Arsuaga’s Nissan, Millás realises that the palaeontologist “experiences sudden bursts of sadness that he sometimes conceals beneath an ironic demeanour, and sometimes beneath passing bad moods. I think the idea that life is absurd bothers him.”

Aruaga’s tragic sense entends to the species. We are the self-domesticating species: “To the Neanderthal,” he says, “the Sapiens must have seemed like a teddy bear.” We have evolved social complexity by shedding the adult seriousness we observe in less social mammals. (“I’ve been to Rwanda, looking at old gorillas,” says Aruaga, “and I can assure you they don’t play at all, they don’t laugh at anything.”) Over evolutionary time, we have become more playful, more infantile, more docile, and we have done this by executing, imprisoning and marginalising those who exhibit an ever-expending list of what we consider anti-social traits. So inanity will one day conquer all.

I wish Millás was a less precious writer. Very early on the pair arrive at a waterfall. “What had we come here for?” Millás writes: “in principle, to see the waterfall, and perhaps so the waterfall could see us, too.” Such unredeemable LRBisms are, I suppose, a form of protective coloration, necessary for a novelist and poet of some reputation: an earnest of his devotion to propah lirtritchah.

It’s when Millás forgets himself, and erases the distance he meant to maintain between boffins and scribblers, that Life becomes a very special book indeed: a passionate, sympathetic portrait of one life scientist’s world view.

Flame brightly and flame out

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Reading Kindred by Rebecca Wragg Sykes for New Scientist, 19 August 2020

How we began to unpick our species’ ancient past in the late 19th century is an astounding story, but not always a pretty one. As well as attaining tremendous insights into the age of Earth and how life evolved, scholars also entertained astonishingly bad ideas about superiority.

Some of these continue today. Why do we assume that Neanderthals, who flourished for 400,000 years, were somehow inferior to Homo sapiens or less fit to survive?

In Kindred, a history of our understanding of Neanderthals, Rebecca Wragg Sykes separates perfectly valid and reasonable questions – for example, “why aren’t Neanderthals around any more?” – from the thinking that casts our ancient relatives as “dullard losers on a withered branch of the family tree”.

An expert in palaeolithic archaeology, with a special interest in the cognitive aspects of stone tool technologies, Sykes provides an fascinating and detailed picture of a field transformed almost out of recognition over the past thirty years. New technologies involve everything from gene sequencing, isotopes and lasers to powerful volumetric algorithms. Well-preserved sites are now not merely dug and brushed: they are scanned and sniffed. High-powered optical microscopes pick out slice and chop marks, electron beams trace the cross-sections of scratches at the nano-scale, and rapid collagen identification techniques determine the type of animal from even tiny bone fragments.

The risk with any new forensic tool is that, in our excitement, we over-interpret the results it throws up. As Sykes wisely says, “A balance must be struck between caution and not ignoring singular artefacts simply because they’re rare or wondrous.”

Many gushing media stories about our ancient ancestor don’t last beyond the first news cycle: though Neanderthals may have performed some funerary activity, they didn’t throw flowers on their loved ones’ graves, or decorate their remains in any way. Other stories, though, continue to accumulate a weight of circumstantial evidence. We’ve known for some years that some Neanderthals actually tanned leather; now it seems they may also have spun thread.

An exciting aspect of this book is the way it refreshes our ideas about our own place in hominin evolution. Rather than congratulating other species when they behave “like us”, Sykes shows that it is much more fruitful to see how human talents may have evolved from behaviours exhibited by other species. Take the example of art. We may ask whether the circular stone assemblies, discovered in a cave near Bruniquel in southern France in 2016, were meant by their Neaderthal creators as monuments? We may wonder, what is the significance of the Neanderthal handprints and ladder designs painted on the walls of three caves in Spain? In both cases, we’d be asking the wrong questions, Sykes says: While undoubtedly striking, Neanderthal art “might not be a massive cognitive leap for hominins who probably already understood the idea of representation.” Animal footprints are effectively symbols already, and even simple tracking “requires an ‘idealised’ form to be kept in mind.”
Captive chimpanzees, given painting materials, enjoy colouring and marking surfaces, though they’re not in the least bit invested in the end result of their labours. So the significance and symbolism of Neanderthal art may simply be that Neanderthals had fun making it.

The Neanderthals of Kindred are not cadet versions of ourselves. They don’t perform “primitive burials”, and they don’t make “proto-art”. They had their own needs, urges, enjoyments, and strategies for survival.

They were not alone and, best of all, they have not quite vanished. Neanderthal nuclear DNA contains glimmers of very ancient encounters between them and other hominin species. Recent research suggests that interbreeding between Neaderthals and Denisovans, and Neanderthals and and Homo sapiens, was effectively the norm. “Modern zoology’s concept of allotaxa may be more appropriate for what Neanderthals were to us,” Sykes explains. Like modern cattle and yaks, we were closely related species that varied in bodies and behaviours, yet could also reproduce.

Neanderthals were never very many. “”At any point in time,” Sykes says, “there may have been fewer Neanderthals walking about than commuters passing each day through Clapham Common, London’s busiest train station.” With dietary demands that took a monstrous toll on their environment, they were destined to flame brightly and flame out. That doesn’t make them less than thus. It simply makes them earlier.

They were part of our family, and though we carry some part of them inside us, we will never see their like again. This, for my money, is Sykes’s finest achievement. Seeing Neanderthals through her eyes, we cannot but mourn their passing.