Charles Darwin certainly did not consider it a sin to kill a mockingbird. The 19th-century English biologist killed many of the birds whilst on board the HMS Beagle survey ship as he traveled around the world. The specimens are more important than you might think and you can see a number of them at “Treasures of the Natural World,” a new exhibition at the National Museum of Nature and Science, Tokyo.

Before he became a world-renowned scientist, Darwin was in training to join the clergy before accepting a position on the Beagle at the age of 22. Darwin collected thousands of specimens of plants and animals during his voyage, including mockingbirds. When he started examining mockingbird specimens from the islands of the Galapagos, he noticed that the birds were different, depending on which island they’d come from.

It’s easy to take evolution for granted these days but, back in the 19th century, most people in the West believed that the Earth was 6,000 years old and that all life on the planet had been created by God. As such, it was sacrilege to imagine that species could change over time. However, Darwin’s observations of mockingbirds — and not so much the finches that later became associated with his theory of natural selection — furnished him with some of the earliest evidence that evolution occurred. He developed his theory of natural selection and, in doing so, built one of the most influential scientific theories of all time.

It therefore goes without saying that Darwin’s mockingbirds are arguably some of the most important scientific specimens ever collected. The exhibition in Tokyo gives visitors a chance to view the actual birds Darwin studied. On display through June 11, the exhibits are part of a trove of some 300 historically important specimens on loan from the Natural History Museum in London.

Other specimens on display include a tortoise Darwin once owned himself and a pigeon skeleton from one of the many pigeons he bred. Darwin bred pigeons to test his ideas about selection, although in this case he was actually studying artificial selection — when traits and characteristics of a species are chosen by a human breeder — rather than natural selection, which can only be found in the wild.

There are also some wonderful Ceroglossus beetles that were collected by Darwin when he was still a young man during a stopover in Chile. Darwin became famous for his observations on birds, which are credited with inspiring his theory of evolution by natural selection, but his first passion was one common in certain kinds of young British gentlemen of his time: beetling, or the collection of beetles.

Yoshihiro Hayashi, director of the National Museum of Nature and Science, Tokyo, was pleased to announce the collaboration with the Natural History Museum. “Many Japanese people know the museum’s collection has excellent stories in scientific, cultural and historical aspects,” he says, “and hope to visit and to see these treasures in our museum as soon as possible.”

As well as the Darwin-related items, the National Museum of Nature and Science, Tokyo is borrowing dozens of other treasures, including one of the most famous fossils of all time — the Archaeopteryx.

I remember seeing this for the first time and being surprised at its size. I think I expected such a famous fossil to be bigger, but Archaeopteryx, which lived 147 million years ago, is only the size of a crow. It has an incredible mix of features common in both dinosaurs and birds, including teeth and fingers ending in claws, but also wings and feathers. The fossil, which demonstrates that birds descended from meat-eating dinosaurs, is an absolute must-see.

Another specimen from the Natural History Museum on display in Japan tells a darker story, but one arguably more relevant to today. The museum is sending a specimen of the Japanese sea lion (called nihon ashika in Japanese), which was hunted to extinction in the 1970s. This species was hunted not only for food (sea lion doesn’t taste so good), but also for blubber to make oil for lamps. Parts were also used in traditional medicine. Thousands of animals were slaughtered, and the destruction of many parts of its habitat due to submarine warfare in World War II didn’t help.

The animal is a reminder that human-driven extinction has been ramping up over the past few decades. We are now driving such widespread habitat destruction that species are going extinct at 1,000 times the natural background rate.

Darwin never visited Japan, nor even, as far as I’ve heard, had much correspondence with scientists in Japan. This is slightly odd, as Darwin was famous for his voluminous correspondence with scientists from around the world. However, given the cultural gap between feudal Japan and Victorian England, it is perhaps not that surprising. Yet he would have been fascinated by these islands.

As the exhibits at the the National Museum of Nature and Science, Tokyo demonstrate, the Japanese archipelago has an extraordinary richness of geology, topography and ecology. The isolation of the islands from the Asian continent has meant that an extraordinary variety of different species have evolved in Japan — it’s one of the reasons that first brought me to Japan as a biologist.

Darwin would have been fascinated by Japan (and he would have appreciated how popular beetle-collecting is here, too). He didn’t quite make it, but many of the items from his collection — including a first edition copy of his book that changed the world, “On the Origin of Species” — are now in Japan.

Rowan Hooper is the news editor of New Scientist magazine. The second volume of Natural Selections columns translated into Japanese is published by Shinchosha. The title is “Hito wa Ima mo Shinka Shiteru” (“The Evolving Human”).

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