During the eighteenth century, natural philosophers—the forerunners of what we would call scientists today—were breaking free from the chains of mythology and asking questions about the origins of life, and particularly about human origins. Instead of turning to mythology—that is, the Christian bible—for answers, they began seeking answers in nature and basing hypotheses on empirical observations. In the mid-nineteenth century, two Englishmen—Alfred Russel Wallace and Charles Darwin—developed the basic concept of evolution by natural selection as a way of understanding human origins.
Alfred Russel Wallace
Alfred Russel Wallace was a professional collector: in the nineteenth century he travelled to exotic places, collected great numbers of different specimens, and brought them back to England to be sold. In 1855, while collecting specimens in Sarawak, northern Borneo, Wallace wrote On the Law Which has Regulated the Introduction of New Species. In 1858, while collecting on the island of Ternate, he came up with the idea of evolution by natural selection. He wrote On the Tendency of Varieties to Depart Indefinitely from the Original Type and sent the manuscript to Darwin. Wallace asked Darwin to show the manuscript to Charles Lyell, one of England’s leading scientists, if it was felt to be important. Darwin was amazed by the manuscript as Wallace’s concepts of evolution by natural selection were nearly the same as his own. Initially, Darwin was devasted, writing: “All my originality, whatever it may amount to, will be smashed.”
In his book The Believing Brain: From Ghosts and Gods to Politics and Conspiracies—How We Construct Beliefs and Reinforce Them as Truths, Michael Shermer writes:
“Wallace was a brilliant synthesizer of masses of biological data into a few core principles that revolutionized ecology, biogeography, and evolutionary theory.”
The solution to Darwin’s fears was put together by Lyell: a joint presentation of the two works at the Linnean Society of London.
Charles Darwin
In July, 1858, the Linnean Society gathered at its new headquarters in London to hear two papers by Charles Darwin and Alfred Russel Wallace in which they jointly announced a theory of evolution by natural selection. While it is common to credit Charles Darwin with inventing or discovering the concept of evolution, many natural philosophers of the late eighteenth and early nineteenth centuries were already talking about this concept. Among those who were looking at evolution at this time were: Erasmus Darwin (1731-1802), the grandfather of Charles Darwin, and Francis Galton; French scientist Georges-Louis Leclerc, comte de Buffon (1707-1787) who rejected Christianity and looked for a different explanation for the origin of the Earth and its inhabitants; Paul Henri Thiry, baron d’Holbach (1723-1789) who rejected the idea of supernatural origins; and, Jean-Baptiste Pierre Antoine de Monet, chevalier de Lamarck (1744-1829) who saw new species emerging through spontaneous generation.
In his book Evolution: The Remarkable History of a Scientific Idea, Edward Larson reports:
“…by the 1820s the conclusion became increasingly inescapable: New species both appeared and disappeared over time. There was simply no place where the newly appearing species could have migrated from: they must truly be new. With traditional faith in a single creation and the permanent endurance of species shattered, the search was on to discover more types of past life.”
Charles Darwin made three basic observations. First, all living things tend to increase their numbers at a prolific rate. Second, in spite of this prolific rate of reproduction, the population of any living creature remains constant over long periods of time. And finally, individuals in any population differ in various features and are, therefore, not exactly alike. Based on these observations, Darwin put forth the idea that those individuals which had the most favorable variations would have the best chance at survival and reproduction. This conclusion would then be refined into a theory of natural selection which implies that the accumulation of favorable variations over a long period of time results in the emergence of new species and the extinction of old species.
In 1859, Darwin published his book, Origin of Species. Edward Larson reports:
“Origin of Species offered a new way of looking at life, and reached audiences far beyond the scientific community. It sold out its initial printing on the first day and was reissued in six revised English editions and eight foreign translations during Darwin’s lifetime.”
In Origin of Species, Darwin viewed the living world as continuously changing with species gradually evolving into new species and other species becoming extinct. In addition,Darwin proposed the idea of common descent: that is, all mammals, for example,share a common ancestor, and so on for all categories of living things. In his book The Making of Mankind, Richard Leakey reports:
“Darwin even speculated that all life, including both plants and animals, might ultimately have come from a common ancestor.”
Regarding the reception of Origin of Species, archaeologist Brian Fagan, in his textbook Men of the Earth: An Introduction to World Prehistory, writes:
“This monumental volume was greeted initially with both effusive praise and vicious criticism, as scientists and churchmen took sides over the issue of the Creation. But gradually the echoes of controversy died away as Darwin’s revolutionary theories were bolstered by more and more field observations.”
James Moore, in his biography of Charles Darwin in The New Encyclopedia of Unbelief, writes:
“In an age when science and society were founded on creationist beliefs, Charles Darwin solved the ‘mystery of mysteries’ of his day: namely, how living species originate. He abandoned the Bible as an authority on creation and explained the origin of species by divinely ordained natural laws.”
In his book The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe Without Design, Richard Dawkins writes:
“Darwin’s answer to the question of the origin of species was, in a general sense, that species descended from other species. Moreover, the family tree of life is a branching one, which means that more than one modern species can be traced back to one ancestral one.”
Within just a few years after the publication of Origin of Species, Darwin’s concept of natural selection as an evolutionary mechanism was accepted by most scientists.
Since the publication of Origin of Species, Darwin’s ideas about natural selection have been widely debated and challenged. However, as new data, new observations, and new scientific methods emerged during the nineteenth, twentieth, and twenty-first centuries, Darwin’s basic hypothesis has not been overturned. In his book Evolution: The Remarkable History of a Scientific Idea Edward Larson reports:
“The subsequent accumulation of facts and observations from branches of biology cemented this theory into a virtual law of science.”
In 1871, Charles Darwin followed up his successful Origin of Species with Descent of Man. James Moore writes: “In his long-awaited Descent of Man (1871), Darwin saw humans evolving physically by natural selection, and then intellectually and morally through the inherited traits of habit, education, and religious instruction.”
Charles Darwin did not discover or invent evolution, but rather his contribution to the theory of evolution was how it worked. Charles Darwin and Alfred Russel Wallace, working independently, arrived at the conclusion that the driving force behind evolution was natural selection. Both Darwin and Wallace had been inspired by the ideas of the mathematician and theologian Thomas Robert Malthus (1766-1834) who had written about overpopulation. Edward Larson writes:
“Applied to plants and animals in nature, Darwin and Wallace independently realized, Malthusian population limits provided a means to generate new species from preexisting ones through the survival of individuals with beneficial variations.”
Human Origins
Human Origins: Sexual Selection
Human Origins: Bipedalism
Human Origins: The Large Brain
Human Origins: Cultural Evolution
Human Origins: The Great Chain of Being
Human Origins: Menopause
Human Origins: Domesticating Fire
Human Origins: Leaving Africa, Ancient Humans (Part 1 of 4)