1996 – Scotland
‘A mammal can be cloned from adult tissues’
Clones are genetically identical individuals produced from the same parent by non-sexual reproduction.
Wilmut and his team at the Roslin Institute near Edinburgh, Scotland, took the nuclei of somatic cells from the tissues of mammary glands of a mature sheep. They took eggs from another sheep, removed their nuclei, which contain DNA, and fused the somatic nuclei with the gamete cells by passing electric pulses through them. The process replaced the DNA of the egg with the genetic material from the mammary tissue. The cloned eggs were placed in a culture dish where they grew into embryos. The researchers cloned 277 eggs, of which 29 grew into embryos. These were transplanted into 13 ewes, acting as surrogate mothers. Five months later one lamb was born. The lamb, Dolly, had no father and its genes came entirely from the udder of a ewe. Dolly the cloned sheep died in 2003.
The mammal cloning experiment has been repeated successfully on other species of mammals. These experiments show that cloning humans is possible, but it has major theological, ethical, moral and social implications.
1859 – England
‘All present day species have evolved from simpler forms of life through a process of natural selection’
Organisms have changed over time and the ones living today are different from the ones that lived in the past. Furthermore, many organisms that once lived are now extinct.
The orthodox view was that of the Creationists. According to the Book of Genesis in the Bible, ‘God created every living creature that moves….’. Against this background, thinkers such as French naturalist Jean-Baptist Lamarck developed a picture of how species evolved from single-celled organisms.
Darwin’s breakthrough was to work out what evolution is and how it happens. His insight was to focus on individuals, not species and to show how individuals evolve by natural selection. The mechanism explained how all species evolved to become well suited to their environment. Later commentators have characterized this idea as ‘survival of the fittest,’ but this was never a phrase that Darwin himself used.
Darwin was influenced by CHARLES LYELL’s newly published book ‘Principles of Geology’, showing how landscapes had evolved gradually through long cycles of erosion and upheaval and by ‘An Essay on the Principle of Population’ written in 1798 by THOMAS MALTHUS.
The publication of Darwin’s book ‘On the Origin of Species by Means of Natural Selection’ in 1859 generated social and political debate that continues to this day. Darwin did not discuss the evolution of humans in this book.
In ‘The Descent of Man’, published in 1871, he presented his explanation of how his theory of evolution applied to the idea that humans evolved from apes. In modern form the theory contains the following ideas:
members of a species vary in form and behaviour and some of this variation has an inherited basis
every species produces far more offspring than the environment can support
some individuals are better adapted for survival in a given environment than others
this means that there are variations within each population gene pool and individuals with most favourable variations stand a better chance of survival – the survival of the fittest.
the favourable characteristics show up among more individuals of the next generation
there is thus a ‘natural selection’ for those individuals whose variations make them better adapted for survival and reproduction.
the natural selection of strains of organisms favours the evolution of new species, through better adaptation to their environment, as a consequence of genetic change or mutation.
Knowledge of DNA has enriched the theory of evolution. The modern view is still based on the Darwinian foundation; evolution through natural selection is opportunistic and it takes place steadily.
1903 – Russia
‘A conditioned reflex is a learnt response to an environmental stimulus’
The process of learning to connect a stimulus to a reflex is called conditioning.
An innate or built-in reflex is something we do automatically without thinking (such as moving our hand away from a flame).
1980 – Switzerland
‘Scanning Electron Microscope’
If a needle charged with electricity is placed extremely close to the surface of a metal or semi-conductor a miniscule but measurable electric current, known as a ‘tunneling current’ will leap the gap. This current is extraordinarily sensitive to the width of the gap. The size of the tunneling current therefore reveals the distance between the needle tip and the surface.
1929 – UK
‘First identification of an antibiotic – the discovery of penicillin’
The chance discovery of a mould in 1928 led to the development of a non-toxic drug, which is used to combat the bacteria that infect wounds.
Whilst Paul Erlich (1854-1915) worked in Germany to produce a ‘magic-bullet’, a compound or dye that could stick to bacteria and damage them, Alexander Fleming’s chance discovery of the antibacterial properties of the mould Penicillium notatum led him to conclude there was a chemical produced by the mould that would attack the bacterial agents of disease.
Whilst searching for a naturally occurring bacteria-killer, Fleming’s experiments were concentrated on the body’s own sources, tears, saliva and nasal mucus.
The chance discovery of the anti-bacterial properties of Penicillium notatum was not developed commercially until World War Two over a decade later.
1865 – France
‘Many human diseases have their origin in micro-organisms’
1862 – ‘Memoire sur les corpuscles organises qui existent dans l’atmosphere’ (Note on Organized Corpuscles that exist in the Atmosphere) – Puts an end to centuries of debate on the theory of spontaneous generation.
Although a chemist, Pasteur is best remembered for his contributions to medicine. His name is used to describe the process of ‘pasteurisation’.
Pasteur proved that living microorganisms cause fermentation. Previously scientists had assumed that fermentation was a chemical process.
Pasteur showed that the alcohol in fermentation was made by the yeast microbe. He also realised that when fermentation went wrong it was due to other germs.
In 1863 he showed that brief, moderate heating of wine and beer kills germs, thereby sterilizing the foodstuffs and ending the fermentation process. The process now known as pasteurisation is still used in the food industry.
His investigations led him to believe that microorganisms could also cause disease in humans. Pasteur realized the dangers of infection, but the English surgeon JOSEPH LISTER (1827-1912) is credited with developing and systematizing the notion of antiseptic surgery so that operations could be made safer if an ‘antiseptic’ procedure was introduced to destroy microbes and curb the infections that followed wounds or surgery.
In 1876, Pasteur confirmed the findings of ROBERT KOCH’s discovery of the anthrax bacillus. After EDWARD JENNER’s breakthrough in the development of vaccination against smallpox, little had been done to take advantage of the potential of this treatment against other disease.
In 1882 Pasteur successfully applied his discovery of vaccination by attenuated culture of microorganisms to anthrax and in 1885 to the treatment of rabies in humans.
On 14 November 1888 the Pasteur Institute opened in Paris.