[In late 1996] in a statement to the 80-strong Pontifical Academy of Sciences, the Pope accepted that the overwhelming volume of experimental evidence in favour of Charles Darwin's theory of evolution could no longer be ignored. "Observational sciences describe and measure with ever-increasing precision the multiple manifestations of life and inscribe them in an [evolutionary] timescale," he said.

But how have our views of the man himself changed? Most modern accounts see him as a gentle genius ahead of his time, a reluctant visionary set apart from contemporary ideas about biological transformation. But some historians question these popular versions of Darwin's life and thought.

The profundity of Darwin's theory of evolution by natural selection is belied by its apparent simplicity. The message Darwin took from Malthus' Essay on the Principle of Population was that creatures have far more progeny than can possibly survive, given the finite resources available. This leads to competition among the progeny for resources. As a result, only a few will survive long enough to reproduce in their turn -- but how are these few chosen? Progeny vary slightly from their parents and from one another. Survivorship would be determined by the suitability of a given variety to the prevailing environmental circumstances. This is Darwin's key insight, "natural selection." As the environment changed, so would the varieties most suited to its demands. Over time, the proportions of different varieties in a species would change, and one species would change, very slowly, into another.

Apart from Malthus, Darwin's other great influence was the epic Principles of Geology by Charles Lyell (1797-1875). Lyell showed that the age of the Earth could be measured in hundreds of millions of years. Even though we now know this to have been an underestimate by an order of magnitude, it is still very much older than the few thousand years suggested in the Bible. This, reasoned Darwin, would allow the evolution of the whole kingdom of nature from primeval beginnings, by the gradual process of evolution by natural selection.

But Darwin had problems. The modern science of genetics was unknown in Darwin's day, and without the particles of inheritance we no now as "genes," inheritance was regarded as a somewhat haphazard blending of parental traits. This, Darwin reasoned, would tend to make every species somewhat uniform in character, in the same way that blending paint of different colours always ends up as a nondescript grey-brown sludge.

Darwin never solved this problem, and a few years after his death, his ideas were in danger of becoming an outmoded footnote. It was only after the "rediscovery" of the classic work of Gregor Mendel (1822-1884) at the turn of the century, and the fusion of natural selection with quantitative genetics, the "modern" theory of evolution came into being. [Note:It was during attempts to reproduce Darwin's genetic experiments with garden plants that Mendel's work was uncovered. Darwin had recorded the same 3:1 ratios in his notebooks as did Mendel but, being relatively poor at mathematics, didn't recognize, as Mendel did, the discrete binomial distribution present within it.]

One of the consequences of natural selection is its randomness. Natural selection is blind to the past and the future, and works with the material available. It does not work like a breeder of domestic animals or plants, with a defined end in view. It is not "progressive" -- and trends or directions that we see in evolution are imposed by us, after the fact, in our quest for patterns and for meaning. Prominent present-day Darwinians, such as Stephen Jay Gould of Harvard University, have emphasized this non-progressive, random nature of evolution.

But given Darwin's limited knowledge of the mechanisms of heredity, we may wonder whether Darwin thought in the same way about evolution as scientists do today.

In The Meaning of Evolution, a controversial look at evolution, historian Robert J. Richards of the University of Chicago argues that Darwin was a man of his time: his early ideas about evolution owed much to the biology of the 1820s and 1830s, in which evolution was seen as progressive. Our modern view of Darwin as a secular saint, strangely ahead of his time, is mistaken and revisionist.

The problem is that the word "evolution" has a double meaning. The word comes from the Latin verb evolvere, to "unfold." In biology, it meant the steady acquisition of form of an embryo as it appeared to "unfold" from a formless egg. Early nineteenth-century biologists saw the development of an embryo as a mirror to its position in the animal kingdom, each stage in its development corresponding to some evolutionary stage in the wider world. Of course, few felt that animals had actually transformed in the way that Darwin envisaged -- the transformation was a purely philosophical, even aesthetic, exercise.

Only later, in the middle of the nineteenth century, did the word "evolution" come to mean what Darwin called "descent with modification." Modern biology keeps the two meanings -- embryological and genealogical --- scrupulously separate. But it was not always so. Darwin's German contemporary (and ardent supporter) Ernst Haeckel believed in a mode of evolution (in the genealogical sense) that was progressive, the development of animal form through time being preserved in embryological development. Most biologists today contend that Haeckel was mistaken and view Darwin, as espousing a non-progressive evolution, propelled by natural selection. But as Richards shows, Darwin's early views were deeply coloured by such embryologically motivated ideas.

But what of natural selection? The inherent randomness of this mechanism would seem to stifle any idea that Darwinian evolution is progressive, a point emphasized by Stephen Jay Gould: "An explicit denial of innate progression is the most characteristic feature separating Darwin's theory of natural selection from other nineteenth century evolutionary theories. Natural selection speaks only of adaptation to local environments, not of directed trends or inherent improvement." Richards argues that although Darwin rejected any innate tendency for organisms to develop into every more complex and "improved" forms, the mechanism of natural selection acted as a kind of ratchet: "Natural selection would exert, as it were, an external pull, drawing most organisms to greater levels of complexity and perfection."

By a close study of Darwin's notebooks, Richards further shows that hidden beneath the conventional view of Darwin's emerging theory was a deeper -- older theory based on embryological transformation, the older, original meaning of the word "evolution." As Richards says, "the term 'evolution' is pregnant with its history."

Darwin's life

• 1809. Darwin born [the same day as Abraham Lincoln] in Shrewbury, Shropshire, England. His father Robert was a prosperous physician; his grandfather Erasmus (1730-1802) a well-known physician, naturalist, and poet.
• 1825. Darwin goes to Edinburgh to train as a physician;, following in his parental footsteps. Disenchanted by his studies in less than a year, he pursues natural history instead. He leaves Edinburgh in 1827, without a degree.
• 1828. Unsuited for medicine, Darwin goes to Cambridge to study for the Anglican priesthood.
• 1831. Darwin gets his degree, and instead of becoming a country priest, is offered the position of Captain's dining-companion on the survey ship HMS Beagle on its next round-the-world trip. Darwin's natural history observations on the voyage of the Beagle form the basis of his later evolutionary thought.
• 1836. Darwin comes home.
• 1838. Darwin reads An Essay on the Principle of Population by Thomas Malthus (1766-1834). This book catalysed Darwin's idea of natural selection as a plausible mechanism for evolution.
• 1839. Darwin marries his cousin, Emma Wedgwood.
• 1842. The Darwins move to Down House, where Darwin spends the next 40 years raising his family, writing, experimenting, and building his reputation as a first-class naturalist. He also becomes chronically sick. The cause is still a puzzle.
• 1851. The death at age 10 of his second child, Anne, severely damages Darwin's Christian faith.
• 1859. Fearing that the naturalist Alfred Russell Wallace would be first into print with the idea of natural selection, Darwin is rushed into publishing the Origin of Species. This long book is the résumé of a still longer, incomplete work. The book is an immediate best-seller (it is still in print). The ensuing controversy makes Darwin even more reclusive than ever.
• 1882. Darwin dies. He wanted to be buried privately in the churchyard at Downe, but received a public funeral at Westminster Abbey. This was the only public honour Darwin received -- he was never knighted.