A timeline of scientific discovery
The 1800s to 1890s
1809 – Jean Baptiste de Lamarck (1744-1829) publishes Philosophie Zoologique
Lamarck was one of the first to propose a theory about evolution. He believed that as animals tried to fit into their environment, their efforts produced a bodily change that was then passed on to their offspring. While a popular theory at the time, it was later disproved by Darwin’s ideas about natural selection. One of the classic images used to describe Lamark’s theory of evolution is of the giraffe's neck. Giraffes needed to stretch their necks in order to reach food in taller trees. This effort resulted in longer necks, a feature passed on to the offspring.
1833 – Charles Lyell (1797-1875) and Principles of Geology
The work of Charles Lyell provided the foundation for the study of modern geology and an essential context to Darwin’s ideas about evolutionary change. The realisation that the world was older than previously thought did much to establish one of the significant beliefs formed in the 19th century – the antiquity of humans.
1859 – Charles Darwin (1809-1882) publishes On the Origin of Species
Darwin was not the first to think of evolution, but he was the first to propose a sound scientific theory supported by a huge amount of evidence. Although he formulated his theory while acting as a naturalist on the HMS Beagle from 1831-1836, his concerns about the implications of releasing such a theory led him to delay its announcement for over 20 years. He may have delayed further if not alerted to the work of Alfred Wallace, another British naturalist who had independently come up with a theory on evolution by natural selection. Darwin and Wallace co-announced their theory to the Linnaean Society of London in 1858 and Darwin then published his work On the Origin of Species the following year. This theory was widely misunderstood and mocked by a society which had been taught by the predominant religions of the day that species were created individually by God and unchangeable. Many decades would pass before the theory gained general acceptance. Darwin’s theory is still accepted today, although somewhat modified, and forms the basis of modern evolutionary theory.
1863 – Thomas Huxley (1825-1895) publishes Evidence as to Man’s Place in Nature’ in defence of Darwin
1871 – Darwin publishes The Descent of Man
This publication, released in 1871, contained the detailed ideas regarding human evolution that Darwin had not discussed in On the Origin of Species. Although written without a single pre-human fossil as evidence, he predicted that humans originated in Africa. It would take over half a century before he would be proven correct.
"In each great region of the world the living mammals are closely related to the extinct species of the same region. It is, therefore, probable that Africa was formerly inhabited by extinct apes closely allied to the gorilla and chimpanzee; and as these two species are now man’s nearest allies, it is somewhat more probable that our early progenitors lived on the African continent than elsewhere."
The 1900s to 1940s
1900 – Rediscovery of Gregor Mendel’s breeding experiments (published in 1866) and the formation of the Principles of Inheritance
The Austrian monk Gregor Mendel (1822-1884) discovered that hereditary particles (given the name ‘genes’ in 1909) pass traits from a parent to the offspring. The appearance of the offspring is determined by these genes, not by a ‘blending’ of characteristics as was believed. The work revealed to biologists how evolution worked at the molecular level and provided the scientific basis for variation that Darwin had been unable to explain. Darwin’s original theory could now be modified and adapted to fit in with this new evidence.
1942 – Julian Huxley publishes The Modern Synthesis
Huxley’s work outlined the role of genetics and ecology in natural selection. He believed that these operated at the core of evolutionary change, an idea that became widely accepted.
1947 – American chemist Willard Libby introduced his work on carbon-14 dating
This discovery revolutionised science, particularly in the fields of human studies. It was first used to provide accurate dates of up to 40,000 years old on European sites. New techniques would soon be developed that worked on the same principles of radioactive decay in other elements and would prove to be more useful in dating older sites.
The 1950s to now
1953 – James Watson and Francis Crick reveal how genes are inherited with their discovery of the double helix shape of DNA.
1960s – Introduction of biochemistry to the field of human evolution
Prior to the 1960s, anthropologists believed that the common ancestor of humans and apes lived about 15 million years ago. This placed humans at a comfortable distance from their closest living relatives, and hence from the entire animal kingdom. The scientific advances in the 1960s would change all of this. Biochemists discovered that they were able to compare the molecules of apes and humans, providing a more accurate measurement of relatedness. The results showed that there were only very small differences between these molecules and that this reflected only a short amount of time since apes and humans diverged from a common ancestor.
The differences between the molecules are caused by mutations in DNA. Knowing the approximate rate at which mutations occur, scientists were able to calculate that the human-line split from the ape-line only five to seven million years ago. This created huge controversy at the time between biologists and anthropologists, a controversy which raged for over a decade before further studies supported the claims of the biochemists. Today no one doubts our close genetic relationship to the other living apes.
1980s – Improved technology, such as CT scans, MRIs (magnetic resonance imaging) and DNA analysis, allows scientists to develop new methods of interpreting fossils.
The study of human evolution has become a multi-disciplinary field.
2003 – Completion of The Human Genome Project (with final papers published in 2006)
This landmark project identified all the approximately 20,000-25,000 genes in human DNA and determined the sequences of the 3 billion chemical base pairs that make up the DNA. From an evolutionary perspective, this project helps identify what makes us human, how we are related to other organisms and what part of our DNA has changed or mutated over time.
2009 – First draft of the Neanderthal genome announced
Comparing the human and Neanderthal genomes with that of our closest living relative, the chimpanzee, may reveal which genes changed very recently giving modern humans an edge over Neanderthals.
2010 – Publication of the first detailed analysis of the Neanderthal genome
Of key importance was the discovery that Europeans and Asians share 1-4% of their DNA with Neanderthals but Africans do not (previous studies on the mtDNA showed no signs of interbreeding between the species). This suggests modern humans and Neanderthals interbred after moderns left Africa and before they spread to Europe and Asia – the most likely location was the Levant, an area both species occupied about 80,000 years ago.