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  • Writer's pictureAryan Shah

Why past species determine future theories.

Updated: Jun 30, 2021

Watch the full interview on Youtube here

Listen to the episode on Spotify and Apple Podcasts!

Palaeontology is often walked upon as a dead subject by many

but what if I told you that by investigating further some of its specificities, we can begin to understand just how relevant it is in the real world and how it can change the way we think about life as we know it.

I had the privilege to chat with Dr. Zerina Johanson on 'The EarthSci Show' about her line of work and what the benefits are of doing what she does.

Dr. Johanson is a researcher at the Natural History Museum in London at the Earth Sciences department, specialising in early vertebrate evolution and development. In my discussion with Dr. Johanson, we addressed some key questions that we thought were crucial for people to understand and comprehend the value of specificities within Palaeontology.


Questions we need to answer

1. By researching the development of the vertebrate skeleton, does this provide any key insights into how vertebrates may evolve further in the future, given the current climate?

Vertebrates are defined as having a backbone - and something that I was unaware of, was the impact of ocean acidification on the vertebral column of chondrichthyans (cartilaginous fish), the fact that the mineralisation process in the cartilaginous backbone is increased as the acidic contents of seawater increase. This has drastic impacts therefore on the swimming patterns and buoyancy of such fish. Dr. Johanson also highlights that as the Earth's climate continually changes, we can then use this critical piece of information to predict how chondrichthyans may evolve in the future as their swimming patterns fluctuate too - allowing us to predict migration patterns, feeding patterns and the dynamics of future marine ecosystems to a greater extent than previously imagined.

2. What do you think are the benefits of researching and finding more about how chondrichthyan dentition formed?

Again, I was totally surprised by Dr. Johanson's response to my question, because I had never imagined such a wide potential in medicine of researching a niche element of Palaeobiology. Dr. Johanson describes a study done involving understanding the genes responsible for such rapid and continuous

tooth replacement in animals such as sharks, rays and skates.

This means that we can then implement such genes into humans in the future by genetic manipulation or gene editing, providing several benefits for bone growth and cosmetic purposes in dentistry too. Dr. Johanson emphasises the potential of specific stem cells that allow us to unlock their uses for our benefit in the future,

especially if we can control or speed up the process of such stem cells when we desire.

3. What impact do you think the Hangenberg or Kelwasser event at the end of the Devonian period had on Gnathostome radiation in particular?

The famous Devonian extinction event is known to have exterminated many beautiful fish species such as the Placoderms (armoured fish), but those that were badly affected but did manage to survive were the Acanthodians (spiny sharks), the Sarcopterygians (lobe finned fish). However, the Tetrapods (four legged animals - descendants of Sarcopterygians), Actinopterygians and the Chondrichthyans survived the Devonian extinction and have thrived to this day. So, as we can see, some fish species did well and some didn't, but what Dr. Johanson emphasised, is that the extinction of specific species such as the Placoderms provided new ecological niche-oriented opportunities for its prey such as the sharks (chondrichthyans), allowing them to rise to the top of the food chain as we can see today. In addition, the Tetrapods flourished from water bodies onto land.

I strongly believe that the success of the Tetrapods would have been hindered by the existence of Placoderms (and their apex predatory status) into the Carboniferous era.

By removing the predator, the number of prey are expected to and usually increase – basic ecosystem dynamics. This allowed the bony fish to dominate the planet as the most abundant fish we see today.

So, as you can see, an extinction event was needed to see the very diversity we are familiar with today.

4. What do you think would have happened if such events didn't happen 365 million years ago? Would our oceans be completely different or similar to what we see today?

Both Dr. Johanson and I agree that we would love to see our favourite extinct fish, Dunkleosteus terreli in the flesh, suggesting that its mere presence would change the focus away from sharks in nature documentaries around the world.

However, besides from appearing on TV, Dr. Johanson believes that the Placoderms, considering how successful they were from the Silurian to the Devonian period, they would have continued to reign over the other fish species to this day perhaps competing with those fish that we consider dominant - such as the bony fish and the cartilaginous fish.

5. Do you think that with the advancements in technology that we see today such as CT scans and morphometrics, this gives a better insight into the past or into the future?

Such exponential technology can be used to better understand the past and therefore help influence our decision about what conservation methods could be employed in the future and also whether any similar events or climatic changes that have already occurred will happen in the future and how to deal with them appropriately. Not only this, but such technologies allow us to dig deeper and investigate further how and why a specimen works the way it does, such as using CT scanning to differentiate between bone and rock,

allowing us to understand the morphology of specimens to a greater extent than before.

There is so much we can now do virtually like manipulating fossils to our will, testing them at different stress and strain levels too. So, by reducing human error to a large extent, such tech can provide much insight into the past, influencing theories about the future.

6. How important are biomechanics in the grand scheme of things in understanding more about our origins as fish and the future of life on Earth?

Dr. Johanson argues that most of the interesting evolutionary events to do with the vertebrate physiology have already occurred in the past, (such as the development of the neck, brain and our muscles, why we walk and how) but to understand them deeply and why they are there and how exactly they came to be, we need to delve into the biomechanics which involves utilising specific software , allowing us to conduct specific analyses such as Finite Element Analysis (FEA) by understanding the Newtonian mechanics and maths behind fossil specimens. It is in my opinion one of, if not the most important way to determine the motion and lives of extinct taxa.

It's easy enough to say, "oh there's a joint there, it must move up and down", but it comes down to biomechanics to look into it more deeply and seeing whether there are important differences present.


So, as you can see here from my chat with Dr. Johanson, past species like the Placoderms or prehistoric sharks can allow us humans to determine future theories of life on Earth by looking at the biomechanics of them, utilising the best technology we have available to us today and also by conducting critical analyses of specificities such as the key mineralisation process in the chondrichthyan vertebral column or the gene control of tooth replacement. Whilst I still think there is an immense amount of work still needing to be done to make great change in the field of Palaeontology, I really do feel from my discussion with Dr. Johanson, that providing key insights into how we can better the lives of humans and of the remaining vertebrates on Earth has been in motion for a while now and is inevitably going to improve as time increases.

Thank you once again to Dr. Zerina Johanson (Researcher, Earth Sciences department, Natural History Museum, London) for her time.


Dental lamina as source of odontogenic stem cells: evolutionary origins and developmental control of tooth generation in gnathostomes - G. Fraser et al

Ocean acidification and warming affect skeletal mineralization in a marine fish – Di Santo et al -

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