With all the celebrations of Darwin's two hundredth birthday around the world, three points are coming up again and again. First, how central his ideas are to our pressing concerns about climate change and the other critical impacts humankind is now having on global biodiversity. Second, how difficult governments and many other bodies are finding it to recognize what Darwinian science is now telling us so urgently about the pace of change and the dangers ahead. And third,  how greatly we need to build the Darwinian  understanding and share it with others, if we are all to agree on effective action to avoid ecological disaster.

Until recently, Darwin has been  seen as a remote and forbidding figure with a chilling message about life on earth. Interest is now growing  in the man and his life. In meetings with conservationists, teachers and pupils in Brazil,  Galapagos and now here in South Africa, I’ve found an enthusiasm for Darwin's years on the Beagle voyage. Students, artists, poets and musicians are also exploring Darwin's later life at Down House in England, and it is increasingly clear that all  Darwin’s insights can be explained vividly and interestingly through what he did on his travels round the world and then around his  home in the English countryside. This is proving a worthwhile way to use his heritage for understanding,  and themes are being developed in exhibitions, drama, films and many other treatments. 

Reading Darwin's journal of  the Beagle voyage, we see what an adventurous young man he was and how he enjoyed everything he was able to experience, except of course the sea sickness!  Cape Town has its own fascinating part in the Beagle story with his visit in 1836 on the  homeward  leg, just as he was beginning to think through what he'd learnt from his collecting on the voyage, and focus on the possibility that species might change.  Wilmot James and Raj Ramesar's  Darwin Trail is a wonderful resource for education and tourism. There are exciting possibilities for linking it with other Darwin trails being blazed in the places he visited in Brazil, Galapagos and Australia, and also perhaps with his daily walks on his "thinking path" in the countryside around his home, for a view of his insights that can be shared on the web and young people around the world can then  join in developing.  If a number of Darwin trails can be linked together in this way, it will be excellent to be able to show from Cape Town, for instance,  what  Darwin saw of the remarkable geology of the Cape and how geology can provide a foundation for the understanding of the history of life on earth and the development of humankind.  I was thrilled last week to stand on Paarl Rock,  see what Darwin saw when his Khoikhoi guide brought him there in 1836, and hear a striking explanation of what the two huge granite domes would have revealed to him about the formation of the earth's surface. It will then also be wonderful to show from the Cape's fynbos what Darwin saw of the uniquely rich plant life of the Cape Floral Region which will be so significant for UNESCO’s  International Year of Biodiversity  in 2010, our global stocktaking  after the Rio Earth Summit in 1992 and Johanesburg in 2002, and to suggest how his evolutionary theory helps to explain the outstanding beauty and diversity of the fynbos flora.   And in Cape Town it is also specially interesting to read Darwin's comments about all the different kinds of people he met here, and  about his friendship with his guide, one of the ‘ill-treated aborigines of the country’ as he wrote,  bearing in mind his deeply-held belief in the unity of the human species and his eventual suggestion, now generally accepted, that our species stemmed from  Africa.

I talked at the Darwin200 conference in Cape Town last week about  how  Darwin’s later work in England developed from his Beagle experiences. As he thought through the implications of his evolutionary thinking, he slowly developed the new vision of life on earth which has transformed our understanding of our place in the living world as full members, not temporary visitors, who need  to concern ourselves about  its fate because its fate will be ours.

Darwin developed his vision with his own fresh approach to the science of life,  starting  with the issue of man and animal at  the moment when he first realised that we might be closely linked. As soon as he saw the possibility, he thought about how to test it. He went to London Zoo and met Jenny, a young orang utan who had recently been brought  from Sumatra  and was drawing crowds. Many others found her disquieting, looked for the differences between  man and  ape, and were reluctant to acknowledge the obvious links. Darwin  looked fearlessly for the likenesses; he was fascinated by those he found and returned to Jenny's enclosure later with a hand mirror and a sprig of verbena,  some sweets and a harmonica to see whether she liked "smells, peppermint and music".  She played with them all eagerly, and in such childlike ways that he saw his next step at once. He wrote in his private notebook, "Natural history of babies",  and jotted down a string of games to play with a human infant, each a simple experiment for  a comparison with a baby animal.  The young bachelor obviously couldn't go to any of his friends or relatives who had small children and ask if he could compare them with an orang utan. But soon afterwards  he found  his wife-to-be, Emma Wedgwood, and once they were engaged, he dared to explain his thinking about humans and animals to her. A short time later, she wrote to him that from what he'd said, she believed he'd also only consider her "a specimen of the genus - I don't know what, Simia [monkeys]  I believe. You will be forming theories about me and if I'm cross or out of temper, you will only consider "What does that prove?""  In the event Darwin spared Emma and was a doting father to all their ten children, but as soon as the first, William,  was born, he was able to start on his "natural history" of the infant's development, watching every stage and repeating the game Jenny had played with the hand mirror. These simple, bold experiments at home with his own child clearly confirmed the link he had spotted, the deeply rooted connection with our animal cousins which is so important for our understanding of our common origin and nature.

After all Darwin's writings about natural life and human nature, we look to him now as one of the greatest scientists of all time, but he was never actually a scientist at all if that means laboratories,  white coats, stacks of equipment and teams of research students and post-docs working on technical papers for scientific journals. He never worked in a laboratory or far-away field station. After the Beagle voyage, he did almost all of his scientific work at  his home, around his garden and in the surrounding countryside. He worked closely with his garden plants and the wild plants of the neighbourhood, and was always happiest to be able to show a feature of natural life in a species that would be familiar to most readers rather than a botanical rarity.

Emma  is the unsung heroine of Darwin’s achievement in science. She had doubts and worries about his theory but understood how important his work as to him and loving him as she did, she supported him loyally. A few examples show her patience with what she had to put up with in their daily life. One summer Darwin wanted to see what attracts insects to flowers and persuaded her to give up some of the brightly coloured  artificial flowers she had for pinning to her bonnet so that he could drop a blob of honey in the centre of each, put some fresh leaves around them and stick them in the soil   to watch what insects came to them.  William,  then two and a half, was playing in the garden and spotted the experimental flowers from some way away. He called out  that they weren't real but had been made by his father,  and coming closer, exclaimed that they were from "Mamma’s cap"! Some years later when Darwin was investigating how clover depends on visiting bumblebees to cross-pollinate its flowers, he used pieces of the light muslin Emma had for her summer dresses to cover up some of the flowers in a clump in their meadow, and showed that  no seeds set on those  flowers the bumblebees couldn't reach. On another occasion he wanted an object that was as light as possible to test the extreme sensitivity of an insect-eating plant he was studying.  He took a strand of Emma’s hair which was so slender that it only  just outweighed the very lightest weight on the most sensitive chemists' scales available at the time.  He then made an item just one   six hundredth of that very lightest  detectable weight by cutting off  a six hundredth of the length of the hair, and was pleased to find that  the plant's tendril curled at its touch. Lastly,  around the same time, when he wanted to test his idea for how a remarkable orchid managed to catapult its pollen at passing insects in order to ensure cross-pollination, he built a  working model  of the mechanism using a whippy piece of a whalebone stay taken, we can only guess, from Emma's corset!

Darwin wrote his most important books for scientists, of course, but also quite as importantly and with great care, for the general reader. He wanted everyone to understand the extraordinary new insights he had gained into natural life. A month after The Origin of Species   appeared, he was delighted to hear from a friend that she'd overheard someone asking for it at a station bookstore; the storekeeper had sold out but  understood "it was a very remarkable book" and was restocking.

To help all his non-expert readers, Darwin used his own kitchen garden plants and farmyard creatures for many of his most telling experiments  in The Origin of Species.  He explained his findings about varieties of peas, beans and gooseberries, a fat white Aylesbury Duck, Emma's choice poultry, and tame rabbits and pigeons which the children helped look after.  He showed the web of life by tracing the  ties of dependence and destruction between the clover, bumblebees, field-mice and cats in his meadow. He grew seedlings out of small birds' droppings he'd picked up in the garden to show how organisms can be transported from one place to another. He gave science's  first view of the range of biodiversity in a single area by counting  the different plant species he could identify in a three foot by four foot section of his back lawn which the gardeners had left unmown so that the plants could be recognized when they grew to flower and seed.  He counted twenty different species, an extraordinary number for a small patch where most of us would have recognized only one kind,  undifferentiated grass. 

Darwin had spotted all these points through careful observation around his country home and garden, but he realised that in many cases, the key features for understanding are missed by most people because they are hidden from view in our remoteness from natural life. He wrote about the struggle for existence, the driving force for evolution: "We behold the face of nature bright with gladness, we often see superabundance of food; we do not see, or we forget, that the birds which are idly singing around us, mostly live on insects or seeds, and are thus constantly destroying life; or we forget how largely these songsters, or their eggs, or their nestlings, are destroyed by birds and beasts of prey …" This suggestion that "we do not see, or we forget …" was critical for him because he was convinced that unless the universal struggle for existence "be thoroughly ingrained in the mind … the whole economy of nature with every fact on distribution, rarity, abundance, extinction, and variation, will be only dimly seen or quite misunderstood."

Again, to help to emphasize the universal struggle for existence - a huge task for a writer in Darwin's position, he  highlighted this key process through a single small experiment he'd carried out in an  abandoned strawberry bed in his orchard -  an almost wilfully trivial example to give in relation to the global significance of the point he was trying to show. But the experiment's simplicity and the ease with which it could be understood from everday experience  were its strength, not a weakness. Clearing the soil in March 1857, marking with a stick each shoot that emerged from then on, checking the sticks regularly and removing any whose seedling had been eaten or destroyed, he found that 357 seedlings appeared but only 63 survived, so six out of every seven plants had been killed in the first stage of their life above ground.   Such was the force of destruction, and hence the pressure of natural selection, that Darwin was able to show were playing on the plant seedlings in his quiet orchard  that one season.

In the present crisis of climate change and loss of natural habitats, we all need to have that sure grasp of "the whole economy of nature" that Darwin wrote about,   if we are to succeed in what needs to be done to preserve what still survives. One way is to follow in Darwin's footsteps on the Beagle voyage and learn what he showed us can be learnt from Paarl Rock, the Cape fynbos and so much more along his whole journey around the world. Another way is to follow Darwin at Down House in our own daily lives and experience,  focusing in the ways he did on what we can understand about  natural life and its history  from what  we can observe around us. Fit  the two views together,  and we have a resource for the global understanding we need. Develop that understanding,   and we can save the  wealth of natural life Darwin has helped us to come to value.