There are some ideas that just won’t die. Like the villain in a movie, even when they’ve been shot with the bullets of refutation, scalded by heated discourse, and pushed off into the pool of disproven theories, these ideas still claw their way back, bedraggled and screaming, to attack us one more time.

If there is one idea in palaeontology that typifies this tiresome cycle, it is the resurrection of the dinosaurs. “Can we ever bring them back?” it is so often asked. Despite scientists repeatedly saying no, the question lives on. This is due in part to the rehashing of a handful of studies that seemed for a moment to offer promise of a real-life Jurassic Park, but have all been shown to be flawed.

This month a team from the University of Manchester and National Museum of Scotland hammered another nail into the dinosaur coffin. Their research added to the weight of evidence that any suggestions that “life could find a way” are the result of cross-contamination in the laboratory. The Jurassic Park that people hanker for is unlikely to ever open its doors – and if it did, it would be full of ostriches, alligators and chickens.

In 2005 the apparent discovery of soft tissues preserved in the fossil of everyone’s favourite Hollywood star, Tyrannosaurus rex*, re-ignited the debate on dinosaur resurrection. A team led by scientists in the US reportedly recovered blood vessels, cells and other soft tissue structures.Two years later, a second team claimed to have recovered T rex proteins. The dino specimen was 68m years old, a mere geological sneeze before the dinosaurs – and many other groups of animals – were wiped from the face of the Earth.

Other scientists soon began picking apart these studies: from simply casting doubts to ferociously dismantling the methods, results and conclusions. The authors reinterpreted four of the seven peptides they’d initially claimed belonged to T rex, and soon other teams proved that at least five of the peptides belonged to a chicken (exactly which chicken we’ll never know, but I’m imagining an Aardmanesque villain, hell-bent on scientific obfuscation). Other teams tried to replicate the results but struggled to get traces of breakdown products (not even the collagen itself, but what remains when it decays) despite using all the tricks in the laboratory analysis handbook – mass spectrometic peptide fingerprinting for example.

A computer-generated model of collagen, the main protein in the connective tissue of animals. Photograph: Scott Camazine/Alamy

The consensus? The recovery of dinosaur collagen peptides was either a statistical error, or the result of laboratory contamination.

“Our work set out to identify the collagen fingerprints for both ostrich and alligator, and was not intending to debunk the previous studies,” said the lead author of the new paper, Dr Mike Buckley of the University of Manchester’s School of Earth and Environmental Sciences. “However, we soon realised that our results were pulling the rug from beneath the paradigm that collagen might survive the ravages of deep time.”

Collagen is a structural protein. It is an abundant key constituent of the connecting tissues of animal bodies. We use it in medicine, for reconstructive surgery, bone grafting and cosmetic surgery.

“Collagen was a logical molecule for folks to try and hunt for, as it is a very robust,” the co-author Dr Phillip Manning, also from the University of Manchester, explained to me. “It is a triple helical molecule that, when ‘locked’ in a bony straitjacket, might well have survived.”

This is where the ostrich walks in. Scientists in search of collagen – as well as DNA – from extinct animals use samples from their closest living relatives to analyse alongside the material recovered from the fossils. In the earlier studies of dinosaurs, an ostrich and an alligator had their collagen analysed for comparison. “They both ‘bracket’, in terms of evolutionary history, the dinosaurs,” Manning tells me. “We would expect the proteins of dinosaurs to be somewhere between birds and basal archosaurs [crocodiles and alligators].” The results gathered by Manning and his team showed that the so-called dinosaur collagen was not just similar to these living species; it was identical. “In other words, contamination.”

Buckley concluded: “The 100% match [of ostrich proteins] to the proposed uniquely dinosaur sequences immediately highlighted some of the issues with these techniques, and the caution needed with extraordinary claims made using them.”

So, unless T rex was just a very well-disguised ostrich, we can now say for sure that its collagen peptide sequences remain unknown. But this begs the question: surely it is DNA, like in Jurassic Park, that science needs in order to bring back the dinosaurs, not proteins? Collagen “is a direct function of DNA,” says Manning. “Some proteins appear to survive for at least one order of magnitude longer than DNA. But alas – it’s too many steps away to give us Jurassic Park.”

DNA, the hereditary material in all organisms that carries their genetic blueprints, doesn’t even make it through the first million years after death.



I asked Dr Ross Barnett, a researcher of ancient DNA, why this genetic material doesn’t survive. “DNA is a pretty unstable molecule,” he said. “There are lots of biomolecular bits and pieces that keep it in top condition in the living cell, but after death it rapidly breaks down. The phosphate bonds that form the outer rings of the double helix are prone to hydrolysis [reaction with water], as are the bases. This can split the DNA molecule in two. Oxidation [reaction with oxygen] is also a major player. UV rays cause weird things to happen too. DNA really wants to be broken up!”

The oldest aDNA (ancient DNA) recovered so far is from a horse, dug out of the permafrost in the Yukon, Canada. At 735,000 years old, it is over 65,265,000 years short of the most recent dinosaur fossil.

A 39,000-year-old female baby woolly mammoth from the Siberian permafrost. Photograph: Kazuhiro Nogi/AFP/Getty Images

“One of the reasons that a lot of ancient DNA work has been done on permafrost material whose subzero temperatures keep the DNA fresher for longer. Even continuously frozen, the best guess is that you might be able to recover million-year-old DNA, maximum,” says Barnett.

The Yukon horse DNA was swamped by that of the bacteria and fungi that had fed on the bone post-mortem. Only through comparison with modern horses could the team of researchers pick out small pieces of ancient pony from the vast haystack of microbial DNA. Even with the most perfect preservation, DNA sequences over one million years old would be useless and fragmented.

Barnett adds: “As for amber, the same time constraints apply. All the reports of successful DNA from amber were in the early days of the field, when sterile technique and an emphasis on negative controls and replication were absent. They were amplifying contaminants: either themselves or stuff in the environment.”

Might we ever be able to resurrect these ancient giants? “I understand the desire to bring back non-avian dinosaurs, but it’s never going to happen using DNA sequence, because there is none left. More recent extinctions, which we are more certain were down to us, could have stronger arguments. Something like the thylacine, great auk, or huia could be more manageable, but I don’t think I’d be comfortable bringing something back only for it to live in a zoo to be gawped at.”

Barnett’s view touches on the ethical quandary surrounding the possibility of bringing an extinct creature back to life, particularly in light of the conservation crisis playing out across the planet. Or as he puts it: “We can’t successfully share the planet with elephants, let alone their extinct relatives.”

Tasmanian Tiger, or thylacine (Thylacinus cynocephalus) in captivity, circa 1930. Photograph: Popperfoto/Getty Images

I was struck by the wording in the press release for this recent collagen paper. It said that the previous discoveries of collagen peptides had suggested “there may be hope one day” of “rebuilding dinosaurs”. Is this really something to hope for? Dinosaurs had their day. They aren’t architectural wonders bombed in a war, waiting to be restored. Although the child in all of us wonders what they’d be like in the flesh, I for one am happy with the arrangement between serendipity and evolution that cleared the global decks 66m years ago, setting in motion a whole new radiation of reptiles, birds and mammals.

“Extinction is an inventible consequence of evolution,” agrees Manning. “Once your number’s up, in evolutionary terms, it’s time to move on. On average, a species lasts around two million years.”

”Modern humans have been around for around 500,000,” he says. “We will be lucky to survive another 1.5 million.”

*If you are wondering why no one searches for ancient molecules in less enigmatic dinosaurs, they do: shortly after the T. rex paper, similar collagen peptides were reportedly found in a 78m-year-old Brachylophosaurus. If you’ve heard of that one, you are either a palaeontology enthusiast or have a small child. Suffice it to say that it’s a herbivorous duck-billed dinosaur.

References

Asara JM, Schweitzer MH, Freimark LM, Phillips M, & Cantley LC. 2007. Protein sequences from mastodon and Tyrannosaurus rex revealed by mass spectrometry. Science, 316:280-285.

Buckley M, Warwood S, van Dongen B, Kitchener AC, Manning P. 2017. A fossil protein chimera; difficulties in discriminating dinosaur peptide sequences from modern cross-contamination. Proceedings of the Royal Society Biological Sciences B, 284:20170544.

Orlando L, et al. 2013. Recalibrating Equus evolution using the genome sequence of an early Middle Pleistocene horse. Nature, 499:74-81.



Shapiro, B. 2015. How to Clone a Mammoth. Princeton University Press.