Alfred Russell Wallace: The Grand Old Man of Science

Wallace was born in Usk (now in Wales) in 1823. Though his family were middle-class they struggled financially.

Wallace had to leave school when he was 14. He took a range of jobs, including in a surveying firm and as a teacher.

In 1844 he befriended a keen young naturalist, Henry Walter Bates, who introduced Wallace to the pleasures of insect collecting.

Four years later, the two men left England for South America. Inspired by tales from other travellers, they planned to explore the Amazon and investigate its plant and animal life, making a living by collecting and selling their finds.

Wallace and Bates arrived at the mouth of the Amazon in 1848. The two men split up and Wallace went north by the Rio Negro river, collecting in areas unexplored by European naturalists.

Over four years he collected thousands of specimens - mostly birds, beetles and butterflies - and made copious notes on his discoveries.

The Natural History Museum's collections in London and Tring hold over 2,500 of the bird skins he collected over his lifetime, including some from his Amazon expedition, shown here.

In 1852 he set sail to return to England, but disaster struck in the mid-Atlantic. The ship caught fire and sank, along with virtually all his specimens and diaries.

Wallace survived, but only managed to escape with a small box of notes and sketches, one of which you can see here.

After 10 days in an open boat, the crew and passengers were rescued by a passing ship.

But Wallace was soon planning his next collecting expedition.

Between 1854 and 1862 he travelled 14,000 miles throughout the Malay Archipelago (now Malaysia and Indonesia).

In the eight years he was away, Wallace collected almost 110,000 insects, 7,500 shells, 8,050 bird skins and 410 mammal and reptile specimens.

Among these are more than 5,000 species that were new to science, such as this Wallace's flying frog. This illustration was drawn by Wallace himself.

After his return home, he wrote a book on his travels.

His most popular work was titled The Malay Archipelago, and has remained in print ever since.

Throughout his travels, Wallace encountered an astounding diversity of animals.

He noted how closely related species appeared near to each other, either geographically in space or geologically in time.

Wallace noticed that the species on the Indonesian island of Lombok and further east were similar to those in Australia.

But they bore little relation to the species on the nearby island of Bali and further west.

These birds come from either side of what seemed to be a line . The yellow crested cockatoo is from east of this line, while the Diard's trogon is from the west.

Wallace's experiences led him to discover the theory of evolution by natural selection - independently from Darwin.

He saw how variations within a single species, such as these male Wallace's golden birdwing butterflies, could eventually lead to a new species being formed.

He realised that if the environment changes, individuals that possess characteristics enabling them to cope better with the new conditions will be more likely to reproduce successfully. So these characteristics will gradually become more common in the population.

This is what is known as natural selection, and can eventually lead to a completely new species.

Wallace came to this realisation in 1858, while lying in a fever in Indonesia.

He wrote down his thoughts and sent them to Charles Darwin in England.

Darwin had discovered the same idea many years earlier, but hadn't published it yet.

In science, if independent researchers both make the same discovery, the first to make formal publication is seen as the legitimate discoverer, the one to receive the honours.

The unexpected letter sent Darwin into a panic. He thought he had missed his chance of publishing his work first.

Darwin's friends, Charles Lyell and Joseph Hooker, helped his cause by presenting his work alongside Wallace's at a meeting of the Linnean Society in London.

Wallace, still in Indonesia, was not consulted about this arrangement.

However, when Wallace found out he was extremely grateful. His opinion was that Darwin had the prior claim as he had obviously been working on the theory for a long time.

The next year in 1859, Darwin rushed out a book on the theory, On the Origin of Species. The impact of the book was immense and caused much debate.

Meanwhile, Wallace continued his collecting expeditions in the archipelago and did not return until 1862.

After his return, Wallace published both scientific and popular works on his discoveries.

He was also a staunch advocate of the theory of natural selection, with many of his ideas on the subject agreeing with Darwin's.

As well as natural history, he became interested and wrote on a wide range of other subjects, including politics and spiritualism.

Wallace lived until he was 90, outliving his contemporaries and becoming a grand old man of science.

He had received many public honours and was famous at the time of his death in 1913 .

His fundamental discoveries helped transform the way we understand the natural world and ourselves.

A statue of Wallace, donated in 2013 to commemorate the hundredth anniversary of his death, is on display in the Natural History Museum's Hintze Hall.