In 1842, Queen Victoria went to London Zoo. She was not amused: "The orang-outang is too wonderful… he is frightfully, and painfully, and disagreeably human." A hundred and thirty-seven years later, David Attenborough entranced the world when he cavorted with gorillas in Life on Earth.
What amazed everyone, once again, was just how human they seemed - and, for the gorillas watching, how happy the famous presenter was to be checked for fleas. Far from finding that frightful, most people (and, perhaps, most gorillas) were charmed and delighted.
That great post-Victorian shift in attitude came from that most Victorian figure, Charles Darwin. A hundred and fifty years ago this month, one great stink was about to replace another. In June 1858, the London sky burnt furiously and the sewage in the Thames began to reek, so much so that the House of Commons had its curtains soaked in chemicals to keep the smell at bay.
Soon, the rains came and the Great Stench cleared, but on July 1 an overheated group of moustachioed men met at the Linnean Society to consider important business: to elect a vice-president, to accept a book on grasses, and to read aloud a note, On the Tendency of Species to Form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection by a Mr Darwin and a Mr Wallace (neither of whom was present).
The event had no impact (there was only one comment: that "all that was new was false, and what was true was old"). But a year later came The Origin of Species, this time written by Darwin without the aid of Alfred Russell Wallace.
With it came the greatest intellectual stink of the 19th century. As Disraeli put it: "Is man an ape or an angel? My Lord, I am on the side of the angels. I repudiate with indignation and abhorrence these new-fangled theories." Most of his fellows agreed. Now, though, the idea that Homo sapiens is a shaven ape is both the foundation of modern biology and part of popular culture, where it belongs.
What was the Darwin-Wallace paper all about? Its logic is simple. There exists, within all creatures, variation passed from one generation to the next. More individuals are born than can live or breed. As a result, there develops a struggle to stay alive and to find a mate.
In that battle, those who bear certain variants prevail over others who are less well endowed. Such inherited differences in the ability to pass on genes - natural selection - mean that advantageous forms become more common as the generations succeed. In time, as new versions accumulate, a lineage may become so modified that it can no longer exchange genes with others that were once its kin. A new species is born.
In 1858, almost nothing was known of human evolution. Now, though, Darwin's whole case can be advanced in terms of apes and monkeys, of chimps and gorillas, and of men and women. We know more about our own past than that of any other species. A modern Darwin would turn to our own family of primates for all the evidence he needed.
Our new understanding of genetics makes the case. Every sperm and every egg ever made by all the billions of men and women who have ever lived is unique; a degree of diversity once almost unimaginable. Such variation is the key to the past and to the present - to ancestry and to kinship. It links life into a common web of descent.
The primates cluster together in a group that includes rabbits and flying lemurs, but does not admit horses, dogs or bats. Their kinship is revealed by a certain piece of mobile DNA that hops around the genome. It has been inserted in just the same place in all those creatures, proof that they share a common ancestor distinct from that of all other furry beings.
Chimps are our closest kin. They are not like us in many ways. They are hairy and do not show the whites of their eyes. The animals cannot float in water or cry when upset, do not bother with adolescence and, even in zoos, do not get Alzheimer's disease.
Male chimpanzees seal up their mates with a sticky plug after sex, while men do not. Females publicise the fact that they are fertile (unlike women, who conceal all signs of that crucial moment). Using a laser, we can measure how fast sperm swim.
Those from rhesus macaques, who have lots of mates, swim faster and lash harder than those of gorillas (where one male more or less monopolises the females). Chimpanzee sperm are almost as energetic as those of the macaque, while ours lag well behind (although they do beat the gorilla).
The much-quoted fact that we share 98 per cent of our genes with chimps misses the many bits that have been inserted or removed in the two lines. The real level is around 95 per cent - itself remarkable enough.
We have lost more DNA than the chimp since the split, and the human line is feebler than once it was. We became shaved monkeys because the code for the hair protein no longer functions. Samson lost his strength with his locks, and so did we: the DNA responsible for certain powerful muscles (particularly those in the jaw), is out of action in ourselves, compared with our closest relative.
A chimp-style déjeuner sur l'herbe is also best avoided, for the animals have enzymes that break down the poisons in raw plants that are fatal to us. Chimpanzees need no kitchens, but they have kept many of the taste and smell genes lost in humans, perhaps because they need to be more careful when choosing food.
A closer look at the genes also hints that there has been more natural selection in the chimp line than in our own since the split: one gene in 60 bears the mark of the Darwinian lash, compared to half as many in humans.
And yet, as yet, no chimp has made a television programme. Mankind's success lies not in our bodies, but in our brains. Darwin noted: "There can be no doubt that the difference between the mind of the lowest man and that of the highest animal is immense" - and he was right. Our cortex, the thoughtful bit, is five times larger than that of the chimpanzee. Baby chimps are born with a brain almost as big as an adult's.
Human babies, in contrast, continue to invest in grey matter until they are about two. Certain human brain genes have multiplied themselves when compared to their chimp equivalents. The brain uses a quarter of the entire energy of the body at rest - twice the proportion in chimps.
How can we afford it? We eat no more food than our kin, but we have a richer diet, with more meat and fewer roots, shoots and leaves. As a result, we need smaller intestines: the way to man's mind was through his guts.
That mind made the London sewers that cured the Great Stink, the theory of evolution, Life on Earth, and more. Disraeli was wrong. Man may be an ape, but his brain is on the side of the angels. Just watch Sir David Attenborough to see how.
Charles Darwin and Alfred Russell Wallace's paper outlining the theory of natural selection was a milestone in the history of science - but how did it come about?
In an exclusive video interview, filmed for The Daily Telegraph, Sir David Attenborough discusses their breakthrough with Roger Highfield. Their work, he says, was not only an intellectual triumph - it was "one of the most heartening examples of good behaviour in science".
The idea that all animal life is related had been around since classical Greek times, but Darwin and Wallace suggested, for the first time, a mechanism by which that came about. The two arrived at the idea in very different ways: Darwin worked methodically, using his remarkable ability to make sense of a vast amount of data; Wallace had a brainwave while suffering from fever. He acknowledged the evidence accumulated by Darwin, which ensured the idea would be taken seriously: as Sir David says, "the two men had great respect for one another".
Steve Jones is professor of genetics at University College London. His book 'Coral: A Pessimist in Paradise' (Little, Brown) was shortlisted for this year's Royal Society Prize for Science Books. The main prize was won last night by Mark Lynas for 'Six Degrees: Our Future on a Hotter Planet' (HarperCollins)