Galapagos study a timely reminder of the genius of Alfred Russel Wallace

There was recent news of a study finding that the distribution and evolution of wildlife in the Galapagos Islands had been affected by variation in sea levels, with land animals able to spread between islands that were linked as sea level dropped during ice ages. This follows similar work on Galapagos lava lizards, and in island groups elsewhere.

"Bingo! Sea level is the critical factor in the Antilles," wrote Dr James Lazell, president of The Conservation Agency in the US, in a reply to an e-mail I sent asking for comments on the Galapagos paper. In 1972, Lazell had published a report on lizards of the Lesser Antilles in the Caribbean Sea, including his discovery that there were stronger similarities between lizards on islands that were linked as sea levels fell by up to 100 metres, while isolated populations tended to have evolved into distinct species.

I first met Lazell some years ago as he studied reptiles and amphibians in Hong Kong. Here, too, he found that sea level changes had been important: for instance, Romer's tree frog surely inhabited a coastal plain during the last ice age, but as the sea inundated the plain it became stranded, surviving on just four Hong Kong islands. Lazell used a term to describe such knowledge: biogeography.

While details on sea level changes are relatively recent, biogeography dates back to the 18th and 19th centuries, and was given particular impetus by the man who arrived at the theory of evolution at much the same time as Charles Darwin: Alfred Russel Wallace. And much as Darwin was influenced by his findings on the Galapagos, Wallace drew on discoveries he made on tropical islands, where sea level changes played vital roles in determining species distribution.

Though best known as a co-discoverer of evolution who gained far less renown than Darwin, Wallace was an astonishing man: an explorer, self-taught naturalist, discoverer of new species, a prolific - and outstanding - writer, opponent of eugenics and believer in both women's rights and spiritualism. It's surprising, then, that historian Dr John van Wyhe has lately downplayed some of his achievements - to the great annoyance of entomologist Dr George Beccaloni.

"This is of concern to myself and other Wallace scholars, as there is a danger that van Wyhe's errors will end up being accepted as fact by others," Beccaloni informed me by e-mail. Beccaloni works in London's Natural History Museum, and in 1999 set up the A. R. Wallace Memorial Fund.

Wallace was born in Wales in 1823, and during his childhood surely seemed an unlikely future hero. Financial troubles led to him being withdrawn from grammar school, and he became an apprentice surveyor. In his early twenties, Wallace met entomologist Henry Bates and began collecting insects. This, plus reading books by travelling naturalists such as Darwin, led Wallace to partner Bates in an expedition to Brazil, where they aimed to collect animal specimens that could be sold in Britain.