Fossil mammals behind the scenes

It’s not every day you get to put together one of the world’s most precious jigsaws.

But reassembling the foot of a giant ground sloth is all part of the job for Dr Neil Adams, our Curator of Fossil Mammals. Having documented each bone, he now has to put the Megatherium foot back together again.

It’s a task that’s easy in theory, with photos, notes and even a century-old catalogue to help put everything back in its proper place. However, when working with fossils that are tens of thousands of years old, it’s never quite that simple.

“It’s a slightly demanding exercise,” Neil admits. “I’m not a Megatherium specialist, so I have to rely on multiple sources to put everything back together. But that’s just what we do as fossil mammal curators – we work on ancient whales to shrews, and everything in-between.”

After a few fraught moments adjusting the last fossil bones, everything eventually slots back into place. The newly catalogued foot is now ready to be used by scientists trying to understand more about Megatherium’s life, and why so many large mammals went extinct at the end of the last Ice Age.

These are just some of the many questions that Neil helps to answer every day as part of his work as a curator. But it’s only one small part of his role.

Bones and bugs

Growing up, Neil didn’t even know that his current job existed. It was only after working with museum collections as a university student that he began to discover what being a curator meant and became interested in finding out more.

“As a research student working with museums, you naturally start developing skills in collections management and I was interested in taking things a step further,” Neil recalls. “I did some internships and working with fossils every day seemed like the dream job. There aren’t many permanent curatorial jobs available, so I was very lucky to be able to get this one.”

Neil now finds himself as one of the people responsible for looking after more than 350,000 mammal specimens from the past 66 million years. These range from fossils found in Antarctica to an elephant tooth found during the construction of the Museum itself. Older specimens with mammal-like characteristics are cared for separately alongside the animals they evolved from.

The scope of the fossil mammal collection is so wide that its name is actually a bit of a misnomer.

“Though we’re called the fossil mammals section, not everything here is fully mineralised,” Neil reveals. “We care for mammoth and other Ice Age specimens that still have some of their soft tissues, while we also have the remains of more recent mammals in the taphonomy collection.”

“Taphonomy is the study of how things fossilise, and we have the bones of all kinds of mammals that have been processed, modified or preserved in different ways. For example, hyenas leave quite specific marks on bones they’ve eaten and chewed, so we can compare modern mammal bones to bones from the fossil record to see if something was consumed by an ancient hyena.”

Having soft tissues in the collection means that one of Neil’s most important jobs is pest control. Everything entering the collection has to be inspected as part of a constant battle to preserve the precious specimens – but in historic museum buildings there are always challenges.

Neil and the curatorial team once discovered evidence of past insect pest activity in parts of the taphonomy collection. While there were no signs that the issue was recent, the team had to make sure the insects, and any dormant eggs they might have laid, were dead. This involved putting more than 100 drawers of specimens into an enormous walk-in freezer kept at −30 °C for three days.

When Neil isn’t inspecting the collection or carrying out his own research, he’s fielding requests from scientists around the world. At any given moment, he could be showing researchers around the fossils, supplying records, getting scans made or considering what science can be carried out on the collection itself.

“A big part of my job is taken up with destructive sampling requests,” says Neil. “This is where a small piece of a specimen is taken away to be used for a specific purpose, such as radiocarbon dating, DNA extraction or stable isotope analysis.”

“These specimens are often unique and can’t be replaced, so we have to consider any request very carefully before giving permission. It’s a lot of paperwork, but ultimately it increases the scientific value of the collection and makes it more useful.”

A favourite fossil

“I have so many favourite specimens, but I think this hippo tooth dug up in Trafalgar Square is a particularly impressive fossil,” says Neil. “I’ve previously studied ancient hippos, so I have a soft spot for them anyway, but this specimen also piques everyone’s interest when I tell them about it.”

“It’s fun to think about hippos living in London. It sums up Britain’s prehistoric, warm past in just one fossil.”

The specimen Neil finds most interesting is a Toxodon skull that once belonged to Charles Darwin. Not only does it have links to historic figures, but it has also inspired a lot of scientific research and continues to do so.

“In the 1800s, Toxodon defied classification and explanation,” says Neil. “More recently, we’ve used protein analysis to finally resolve how it’s related to modern mammals. It’s also an important specimen to help understand the extinctions of Ice Age megafauna, which have implications for modern mammals today.”

Dishing the dirt on fossils

Some of the more unexpected specimens in Neil’s care are the field samples. These are bags and boxes of rocks and earth filled during fossil excavations. They can be used to reveal more about an ancient ecosystem.

“Field samples can contain all kinds of things, from the teeth and bones of small fossil mammals and other vertebrates to ancient invertebrates and fossil plant remains,” Neil explains. “The samples often give bigger bones context and can contain important discoveries in their own right.”

Scientists process field samples by gradually washing and sifting all the material through a series of ever smaller sieves, separating everything that doesn’t pass through. They then examine this material under the microscope, picking out any fossils.

Until recently, it was very difficult, if not impossible, to assign small broken bone fragments found during sample processing to a particular species. This is because these fragments don’t have many recognisable features. However, recent research is starting to link these tiny remains to the creatures they came from.

“Researchers at the University of Reading have recently tested some small bones from the samples for proteins. Specific protein patterns are unique to particular animals, so we can start to identify even tiny bone fragments if their proteins are preserved,” says Neil. “It’s less effective on older material, but so far we’ve had success rates as high as 85% from fossil sites that are up to 250,000 years old.”

“In the future, this could mean that what we now think of as unrecognisable shards could reveal much more about what was living in an ancient ecosystem.”

While parts of a field sample are often processed soon after a dig, a large amount can be kept unprocessed. This material is stored so that future researchers can study it using the latest science and technology.

After decades of excavations, the number of field samples in the collection has grown substantially. Neil estimates that there are well over 3,500 boxes and bags, containing more than 40 cubic metres of material – enough to fill about 28 hot tubs!

Eventually, Neil hopes to fully catalogue the field sample collection. This will make it easier for future researchers to use this mountain of material and reveal more about the history of life on Earth.

One of the more major challenges Neil faces in such a large collection is finding everything. The accumulation and movements of specimens over 150 years means that some aren’t where they’re meant to be, while others haven’t yet been catalogued.

Recent projects are helping to bring these records up to date. For example, Ice Age specimens dredged up from the bottom of the North Sea were previously stored in uncatalogued crates. Now they’ve been properly documented and recorded, they’re available for research.

Additionally, high-quality casts of sabretooth cats and dire wolves from the La Brea Tar Pits in California have been rediscovered in the stores. These can now be used for display and outreach activities.

Neil has now been documented their locations in the collections management system, alongside an increasing number of other mammal fossils. Eventually, once everything is recorded, scientists will be able to track down fossil mammals at the touch of a button.

Fossil mammals on the move

The ongoing cataloguing of the collection forms part of the wider NHM Unlocked programme, which is building a new Science and Digitisation Centre at Thames Valley Science Park near Reading. Over a third of all the specimens we look after will eventually be housed there, including the fossil mammals.

As part of preparation for the move, Neil and his team are currently re-examining every specimen in the collection. While large skeletons were often historically registered as single items, this isn’t necessarily how they’ll be packed and moved. In some cases, the team need to inventory each individual bone to make sure everything can be properly tracked and transported.

“It’s not as easy as it might sound,” Neil adds. “One particularly challenging specimen was the skeleton of a Glyptodon, an extinct armoured armadillo relative from South America, that used to be on show in the main hall.”

“It had been recorded as one specimen, but it’s actually made up of bones from more than one animal as well as some casts. Parts of the skeleton are also split between the offsite store and South Kensington, which makes it even harder to keep tabs on. It took a while, but we were finally able to give each piece its own trackable number.”

The work to understand each specimen has fed into the design of the new centre, with measurements used to figure out exactly how much space they’ll need. This will mean that more of the fossil mammal collection can be fully unpacked for the first time, making it much more accessible for scientists studying it.

The collection will also be shared in digital form with everyone who can’t visit in person. Scans are already being used for groundbreaking research and to create 3D-printed exhibition models, with the move set to accelerate the digitisation of the rest of the specimens.

It’s a busy time to be Curator of Fossil Mammals, but Neil takes this in his stride. The jigsaw of the fossil mammal collection is slowly coming together, providing a vision of the future for scientific research.