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The Royal Society of Edinburgh
Great Ideas of Biology
Sir Paul Nurse FRSE
President of the Royal Society
and Director of the Francis Crick Institute in London
Monday 24 February 2014
Report by Matthew Shelley
Nobel Laureate Sir Paul Nurse was welcomed by the President of the RSE, Sir John
Arbuthnott. The geneticist and cell biologist, who spent seven years of his early career in
Edinburgh, looked at the history and interplay between a series of fundamental ideas in
biology which shape our understanding of the nature of life.
Biologists tend to be more comfortable with detail than grand theories, according to Sir
Paul. Yet their work has yielded great ideas fundamental to our understanding of life. His
talk explored the development of four well-established concepts and pointed to a fifth,
which he said has still to be adequately formulated.
1. The cell as the basic unit of life
“In a sense you can consider the cell to be life’s atom,” said Sir Paul. All life is composed
of cells and they are the simplest units which exhibit the characteristics of life. The idea,
like most he discussed, is an old one. It emerged in the 17th Century, when Robert
Hooke, curator of experiments for the Royal Society, discovered plant cells while using
an early microscope to examine a sliver of cork. One story suggests that he coined the
term ‘cell’ because the small rectangular units reminded him of the rooms occupied by
monks in monasteries.
An important leap forward came at the end of the 17th Century, when Antonie Van
Leeuwenhoek first identified single cell organisms. This happened when he used a
microscope to observe the bacteria in matter scraped from between his own teeth.
The next century saw advances in technology and scientific methods, and in 1839 the
German scientist Theodor Schwann stated that the cell is the basic structural unit of life.
Twenty years later, Rudolf Virchow added the recognition that cells are the simplest
living organisms.
These two ideas led to our modern understanding of cells as the basic unit of life that
underpins all reproduction and development. As the regular media stories about stem
cells illustrate, it is an area of biology which continues to be of huge significance.
2. The gene as the basis for heredity
The Ancient Greeks noticed that characteristics are passed between generations.
Nineteenth-Century plant breeders then strove to understand heredity. They had little
success until scientist and monk Gregor Mendel applied rigorous scientific techniques.
Focusing on the pea, he developed the theory that in the first generation after breeding,
one characteristic tends to dominate over another. But the seemingly lost characteristic
re-emerges in the second generation, but is outnumbered three to one by the dominant
one.
Mendel proposed that particles (we now call them genes) are passed on through
breeding which help determine character. Implicit in this was the idea of information
transfer.
Mendel was neglected for 35 years until the start of the 20th Century, when three other
groups reached similar conclusions. The intervening period saw research that placed his
abstract ideas firmly within the realms of scientific observation. This included
observations of chromosome behaviour during cell division, which led to the idea that
they might be determinants of heredity.
The 20th Century brought rapid progress in genetics. In the 1940s, it was shown that
DNA was the key hereditary material. The 1950s saw the identification of the double
helix structure of DNA, and then Francis Crick’s statement of the Central Dogma of
molecular biology, which explains the flow of genetic information through biological
systems.
The gene as the basis for heredity is, said Sir Paul, a truly great idea. It not only allows
us to explain how we are made up (our phenotype), but also has vast implications for
who we are – the balance between biological predetermination and environmental
influence.
3. Evolution by natural selection
This is “a very powerful and beautiful idea; probably the most important in biology,”
according to Sir Paul. The theory states that life evolves and that this largely occurs due
to natural selection. Whilst Charles Darwin contributed enormously to this great idea, it
has a long and complex history. Indeed, his own grandfather, Erasmus (doctor, scientist
and member of the Lunar Society), was amongst those who proposed that life evolved.
Charles was essential because, where others had speculated, he gathered huge
amounts of living and fossil evidence.
Darwin’s 1859 Origin of Species contains one illustration, a tree of life – the first clear
demonstration that all life is related by descent. The idea of natural selection (also put
forward by Patrick Matthew and Alfred Wallace) is simply stated. Darwin observed that
many creatures are well adapted to their environment. He concluded that the best
adapted are most likely to thrive, breed and pass on their characteristics to future
generations. Changes accumulate and eventually give rise to new species.
Natural selection is dependent on cells and genes. Life must reproduce, it needs an
hereditary system, and that system must allow for variability. It is cells and genes that
hold the properties which allow this to happen.
The implications of natural selection go beyond its capacity to explain evolution, said Sir
Paul. Kin selection, and the notion that sacrificing yourself for relatives who will pass on
your genes, takes it into the realm of altruism and morality. And there is also the issue
that as all life is related, humans should be good stewards for their entire extended
family.
4. Life as chemistry
Whilst the theory of evolution tells us where life comes from, the idea of life as chemistry
addresses how it works. An 18th-Century mechanistic concept, it displaced earlier ideas
of “vitalism”. It shows that physics and chemistry can explain life and that it is not a
mysterious other force.
Antoine Lavoisier (the founder of modern chemistry, who was executed in the French
Revolution) was a central figure in the emergence of this great idea, thanks to his study
of fermentation. This led him to recognise that cells carry out chemical transformations,
that these are necessary to the cells, and are expressions of their life.
Explaining life in terms of chemistry involves an understanding that proteins act as
catalysts, transforming one chemical into another. Sir Paul said that this is the basis of
cell structure. He sees cells as “a myriad of chemical microenvironments”, with many
compartments which allow lots of mechanical work and thousands of chemical
transformations to take place simultaneously.
Life as chemistry not only provides an explanation of life, but is the primary paradigm for
understanding diseases – seeing disease happening when something goes wrong with
the chemical reactions. That thinking, in turn, is vital to how the medical and
pharmaceutical industries approach their work to tackle disease.
5. Information and systems
This developing idea sees biology as explicable in terms of information management
and complex systems. Again, it is not new, with Kant having written about biology as
complex systems. But it was the blossoming of the computer era, from the mid-20th
Century, which allowed new theoretical thinking to take place about biology as
information management.
Sir Paul said many biological phenomena can be described as interacting components
(complex systems) and understood in terms of how information flows through them.
These operate at all scales, from neuron systems in brains to whole ecosystems. Sir
Paul concentrated on the cellular, as it is the basis for life.
The aim is to explain higher order biological phenomena such as homeostasis,
communication, reproduction and even physical shape in terms of systems and
information flow. Sir Paul said: “You need to translate the descriptions of the chemical
and physical processes in cells into the underlying systems and the management of
information within that system.” This encompasses the gathering, storing and processing
of information and its use in determining the outputs of the complex system.
One example is DNA, which is only properly understood in biological terms when it is
seen as a digital information storage device. Likewise, some biological systems act
something like electronic circuits. However, they are more sophisticated and versatile
than anything in a computer. Nonetheless, cells, said Sir Paul, are complex chemical
systems which act as logical computational machines.
Biological systems are also dynamic, which radically increases their information
management capacities. Whilst this means they can be hugely sophisticated, it is clear
that they are not intelligently designed. They have many redundant features from the
distant evolutionary past and have many imperfections.
In summing up, Sir Paul said that the issue of complexity may take biology into new
areas of abstract theory, as happened with physics and chemistry. He concluded by
saying that information and systems are likely to be hugely illuminating for biology in the
future.
Questions and Answers
● When will biology accommodate thermodynamics?
According to Sir Paul, it is important that biology is explained in terms of physics and
chemistry. But he speculated that the next advances in biology may come from the
better understanding of information and complex systems, rather than through
chemistry.
● A substantial minority do not accept evolutionary theory; does the fifth great idea let
them off the hook?
Evolutionary theory is uncontroversial in many places, except where faith and dogma are
treated as equivalent or superior to evidence-based science. Hopefully, this will diminish
as science reveals even more about life and the Universe.
● Of all the ideas, which is the greatest?
Evolution by natural selection is a beautiful idea. It explains how complexity can arise
without creationism and is very rich in its implications.
A Vote of Thanks was offered by Sir William Stewart FRSE (past President of the RSE).
Opinions expressed here do not necessarily represent the views of the RSE, nor of its Fellows
The Royal Society of Edinburgh, Scotland’s National Academy, is Scottish Charity No. SC000470