On the trail of the evolution of mammals

Woman sitting on top of a large, layered rock formation

Elsa Panciroli recently joined the Museum research team as an Early Career Leverhulme Research Fellow. Elsa is a Scottish palaeontologist, whose studies focus on the early evolutionary origins of mammals, working extensively on fossils from the Isle of Skye. Here she tells us how her work will combine studies of mammal evolution with stunning new fossil finds from Scotland.

We are mammals. This means we share a common ancestor with creatures as different as hippos, opossums and platypuses. All of us are united in one taxonomic group by a suite of characteristics in our bodies, but principally, that we feed our young on milk. Every mammal from a baboon to a blue whale produces milk for their offspring, and this makes us unique among animals alive on Earth today.

Wareolestes rex is a Middle Jurassic mammal, illustrated here by Elsa Panciroli

But not all mammals bring their young up in the same way; raising a kitten is nothing like raising a kangaroo or a platypus. Kittens are born stumbling around with their eyes closed, while platypus babies are laid in eggs – yes eggs – and when they hatch they look like little scampi. Both are underdeveloped at birth or hatching, but that’s nothing compared to kangaroos. They leave the womb only millimetres in length, and wriggle their way like living jellybeans toward a teat in the marsupial pouch, where they latch on. Only after two months of milk-drinking are they able to hop for themselves and leave the pouch.

The different ways that mammals are born and grow is a huge area of scientific research. But there are still some major questions to answer about the evolution of these growth patterns. When did the ancestors of mammals stop laying eggs? Were they born defenceless, or able to fend for themselves? How quickly did they grow up and how long did they live?

The Rock Hyrax (Procavia capensis) is a terrestrial mammal native to Africa and the Middle East

Over the next three years at the Museum, I’ll be looking for evidence in the fossil record to help us try and answer some of these questions. I’ll study living mammals to understand how they are born and grow, combining this information with data from some of the amazing fossils being found on the Isle of Skye. With collaborators in South Africa I’ll try and work out how the ancestors of mammals developed, and what this means for the bigger picture of the origin of mammals as a group.

Alongside my main research I hope to share lots of stories about our fossil past through the museum’s fantastic public engagement programme. I’m also very active on social media, and I write about science for online and in print publications. So if you see me on your next visit to the building, or find me online, feel free to ask about my research! I look forward to seeing you, and sharing more about the elusive and exciting origins of mammals – and ourselves.

Follow Elsa on Twitter at twitter.com/gssciencelady.

Brain washing

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Our next exhibition – Brain Diaries: Modern Neuroscience in Action – opens on 10 March and in preparation we have indulged in a little bit of brain-washing… This article contains an image of a preserved human brain.

One of the first displays visitors will encounter is a ‘wall’ of 23 fluid-preserved mammal brains – from a Short-nosed Bandicoot to cow. The style of jar, with its black bitumen and paint backing, tells us that these were once used for display so it is exciting to put them in the public galleries again. Museum conservator, Jacqueline Chapman-Gray, runs us through the meticulous process she undertook to ensure these brains will look their best for their return to the limelight.

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Cow brain before conservation treatment
A number of the brains had become dehydrated over time as the level of fluid – alcohol – had dropped. These needed to go through a rehydration programme to ensure their long-term preservation. This is more complex than simply adding more fluid to the jar. Instead the alcohol level needs to be increased gradually to avoid damaging the tissues.

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Brains soaking in alcohol
Others had started to detach from their glass mounts, or anatomy labels that marked each of the different areas or sections of the brain had come loose. These were carefully remounted using specialist conservation-grade materials and a steady hand! Three brains had become completely detached and were repaired using a polyester monofilament thread, otherwise known as fishing line.

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Repairing a human brain with a beading needle

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Labels found detached at the bottom of the jar
For the smallest of the brains a normal sewing needle was enough to pass through the tissues but for the larger two either a flexible 10cm beading needle or large 25cm mattress needle was needed. The original threading points were reused wherever possible though in one case this proved to be too difficult, as the tissue was soft and susceptible to breaking. With precision and patience I was able to gently stitch them back into place on the backing plate so they look as good as new.

All of the jars were given a thorough clean to ensure that seals were tight fitting and that the contents were shown off to their best. They were then filled with fluid to 4/5ths from the rim and the brains gently placed back inside.

Lids were sealed with clear silicone and each jar was topped up with a syringe through a small hole in the lid that is there for this very purpose – once full, this hole is also sealed.

Lastly, after the seals had dried, for the final finishing flourish black paint was reapplied to the backs and tops of the jars to provide a contrasting backdrop.

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Ta-dah… the cow brain after conservation treatment
Brain Diaries opens on Friday 10 March and runs until Monday 1 January 2018. Take a look at the website to find out more about the exhibition and accompanying programme of events at braindiaries.org