Seeking Answers From Sharks
New genetic studies suggest that understanding sharks and their DNA could benefit human medical research. The findings not only add to our scientific interest in these predators, but also increase their conservation importance. There is, it seems, much more to sharks than meets the naked eye.
If you’d stepped into the garden of the Augustinian Abbey of St Thomas in Brno (now in the Czech Republic) on a sunny day in the year 1865, you might have been forgiven for missing any clue that groundbreaking science was in action. The variously white or purple blooms of common pea plants Pisum sativum blushed under the studious gaze of a monk, their tendrils reaching like tentacles across the soil to where he stood, lost in his musing. Gregor Mendel and his garden were set to lay the foundations of a branch of science that is changing the world as we know it.
For conservation, Mendel’s humble experiments may now be integral to how we understand disease, manage the effects of climate change for whole populations of animals and trace endangered species around the world. The monk kept meticulous notes on the height of his plants, the shape and colour of their pods, their seeds and the position and colour of their flowers. Over two years, he documented how the offspring in each new generation of pea plants inherited traits from their parent plants; how specific characteristics were passed from one generation to the next. Gregor Mendel set the basic rules for biological inheritance. The principles of Mendelian heredity, as they were later dubbed, laid the groundwork for modern-day genetics, long before anyone knew genes even existed. This unlikely gardener has been logged in the annals of history not for his spiritual contribution as abbot, but as the father of genetics – the study of genes, DNA and evolution.
At about the same time that Mendel was formulating his ideas of heredity, a Swiss chemist was well on his way to discovering DNA. In 1869, Friedrich Miescher, sifting through patients’ pus-coated bandages that had been mailed to him at his request from a local clinic, discovered an entirely new substance that he called nuclein. Just as Mendel’s discoveries of heredity weren’t well accepted during his lifetime, it would take more than 50 years for the gravity of Miescher’s nuclein findings to resonate within the scientific community. Nevertheless, the foundations had been laid and scientists would go on to discover genes, the unit of inheritance passed from one generation to the next that determines some traits of the offspring; and DNA, the deoxyribonucleic acid that carries genetic information.
Today, genetic research opens a new window into how life on earth works. Understanding genes has revolutionised conservation science, where now scientists recognise the importance of preserving genetic diversity in populations so that they are resilient to diseases, catastrophic events or even the murky effects of climate change. Genetics has opened avenues of conservation forensics, like the field of DNA barcoding, which has revealed that more than half of the dried shark fins and mobulid gill plates currently being traded originate from species classified as Endangered or Vulnerable by the IUCN. The conceptual leap from common pea plants growing in an abbey to the conservation of sharks today may seem vast, but for a geneticist the distance between species becomes a relative concept. If Mendel and Miescher could have had any inkling of the long-term potential of their discoveries, they might have sensed what Charles Darwin meant when he said, ’In the distant future I see open fields for far more important researches…’.
To truly appreciate why shark genetics is particularly interesting to scientists today, one has to go back in history much further than Darwin, Miescher or Mendel. Back, in fact, to when most land on earth was amassed into a super-continent called Gondwana and the seas were filled with an astonishing wealth of marine animals. About 450 to 470 million years ago, around the same time that the first plants made it onto land, odd creatures with even more eccentric names, like graptolites, trilobites, brachiopods and conodonts, shared the waters with red and green algae. Sixty per cent of the species in these ancient oceans would go extinct at the end of what palaeontologists dub the Ordovician period, but scientists believe that at some point during this time an arm of the genetic tree branched out, splitting sharks off from bony vertebrates such as the osteichthyes (bony fishes).
