First editions of Darwin's On the Origin of the Species have become key lots to look out for at auction, with some of them bringing six figure sums.

However, it is not just the work for which Darwin is most famous that has proved covetable. His substantial contribution to the narrative of the Beagle's voyage has proved highly desirable to collectors.

It was on this voyage that Darwin's ideas of evolution by natural selection - even though little of this is hinted at in the text and Darwin didn't publish his opinions on that subject for many years.

First edition of Darwin's Voyage of the Beagle

A first edition sold for £21,250 ($33,000) at Christie's last year, reflecting the excitement brought by owning a copy of Darwin's first published work.

However, Bonhams outdid this this week when a copy sold for a stunning $36,600. Perhaps this reflects the fact that Darwin's works are increasingly seen as worthy of investment.

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