Anatomy of a world

Plastic drifting in the ocean is a potential hazard to marine life. How much plastic the oceans can absorb is a question experts do not have an answer to.
Plastic drifting in the ocean is a potential hazard to marine life. How much plastic the oceans can absorb is a question experts do not have an answer to.PHOTO: SHUTTERSTOCK
On the early Earth, clay could have kick-started the process of biochemical diversification that later brought about life as we know it.
On the early Earth, clay could have kick-started the process of biochemical diversification that later brought about life as we know it.PHOTO: SHUTTERSTOCK
The birth of a materpiscis – a prehistoric fish. Placoderms are an extinct group of armoured fish that were the dominant vertebrates on Earth for over 70 million years.
The birth of a materpiscis – a prehistoric fish. Placoderms are an extinct group of armoured fish that were the dominant vertebrates on Earth for over 70 million years. PHOTO: WILDTYPE MEDIA

Nobel laureate Sydney Brenner's new book, 10-On-10: The Chronicles Of Evolution, covers 14 billion years of evolutionary history, from the beginning of time to the rise of mankind and beyond. The project, Dr Brenner's brainchild, was written by 24 renowned scientists. Cheryl Teh brings you some excerpts from the book.

The challenge of the Anthropocene (current geological age)

How much plastic can the oceans absorb, and how much ecological damage can the Earth sustain? What are the boundary conditions within which a safe, stable human society is possible?

We have estimates but we do not have the answers.

The more we understand about environmental impact, however, the more we realise how even the best of human intentions can have disastrous and unintended outcomes.

There is a time lag between society's ability to recognise the magnitude of these problems and the possibilities for mitigation.

Many of the environmental problems we face can technically be solved; what is hindering us is more a matter of political will. We know the alternatives to fossil fuels, plastics and so on, but our trailing ability to steer global governance is in a race with the rapidly advancing consequences of our actions. - Dr J. Stephen Lansing, director of the Complexity Institute and professor at the Asian School of the Environment at Nanyang Technological University, who suggests that planet earth is fast approaching its tipping point.


From clay to the code of life

NEW QUESTIONS

The advent of humans is comparatively recent, perhaps two million years ago. Modern biology began only in 1953, and we still do not understand how our brains work. Science has created many new technologies, and our efforts are likely to exhaust natural resources and change much of the world as we know it. The future is full of new questions. Will genetic engineering allow us to create new sources of food, and will we be able to create new minds in computers? These are new elements in a complex world, and they will bring about new changes.

DR SYDNEY BRENNER, in the book's foreword.

Since only very simple chemical building blocks existed on the prebiotic Earth, what might have kick-started the process of biochemical diversification that eventually enabled the thioester (precursor to life) world, the genetic code and life as we know it?

Enzymes, which catalyse chemical reactions today, were absent, so we need a simpler mechanism.

We think the answer lies in a seemingly humble substance: clay.

Formed through the reaction of silicates with water, clay minerals have layered crystal structures that provide ideal surfaces for molecules to bind to and interact with each other in close proximity.

In fact, we have long used these very properties of clay to speed up chemical reactions in oil refineries and in the catalytic converters found in cars.

Thus, on the early Earth, clay minerals could have played the role of non-enzyme catalysts, helping to bridge the gap between simple combinations of atoms and complex organic molecules. At first, clay could have catalysed the incorporation of carbon dioxide in the atmosphere into organic molecules - a very early version of the photosynthesis we now see in modern plants.

Over time, clay would then evolve the ability to incorporate sulphur, allowing for the formation of thioesters; nitrogen, allowing for the synthesis of amino acids; and finally phosphates, enabling the advent of RNA and DNA.

These intriguing characteristics of clay - which my colleagues and I continue to investigate - could tell us even more about the transition from prebiotic chemistry to the first biological life forms.

Not only that - if life on Earth began in clay, this will guide our search for life on other worlds.

When we scour the surface of Mars for molecular fossils of early life, we should look not only for amino acids and other biochemical molecules, but also for ancient minerals such as iron-rich clays and magnetite. - Dr Hyman Hartman, research scientist, Department of Biology, Massachusetts Institute of Technology.


A salute to our placoderm pioneers

It all began with an unusual tangle of tiny bones near the head of a particular specimen we found at the Gogo Formation in the Kimberley region of Western Australia.

At first, we couldn't figure out what they were, but it turned out to be the most exciting discovery of my entire career. What we were looking at was actually an embryo, an unborn baby placoderm inside a mother fish - undeniable proof that primitive fish were actually having sex.

SCIENTIFIC ODYSSEY

10-On-10 took us on a scientific odyssey that traversed cosmology, chemistry, biology, palaeontology, archaeology, anthropology and sociology.

DR BENJAMIN SEET, executive director of the Biomedical Research Council at the Agency for Science, Technology and Research, who edited the book and wrote its introduction.

Placoderms are an extinct group of armoured fish that ruled the oceans, rivers and lakes of the world as the dominant vertebrates on Earth for over 70 million years.

Once thought to be an evolutionary dead end, they are now recognised as ancestors of us all, developing innovations such as jaws, teeth, paired hind limbs and the first skull with paired plates - effectively 60 per cent of the human body plan.

The fossil we found at Gogo - which we named materpiscis attenboroughi after the English naturalist David Attenborough - belonged to a small group of placoderms called the ptyctodontids.

"As excited as we were about our discovery, it also raised further questions: Did other more common placoderms also have sex? - Dr John A. Long, strategic professor in palaeontology at Flinders University, Australia.

A version of this article appeared in the print edition of The Straits Times on November 10, 2018, with the headline 'Anatomy of a world'. Print Edition | Subscribe