Charles Darwin – Part 2

Charles_Darwin_aged_51


Developing The Theory


When Darwin returned from his voyage on the HMS Beagle he became an instant scientific celebrity, with his various collections of rocks, fossils and zoological specimens earning him acceptance into the scientific establishment. He began writing papers, mainly on geological topics, and conversing with leading scientists of the day.

Megatherum_Groundsloth

As Darwin published accounts of his voyages and analyses of his various finds, he began to conceive of an idea that species are not “immutable”, that they could change over time. When Darwin’s fossils were reconstructed they revealed strange extinct creatures that no longer existed – such as a rodent the size of a rhinoceros and a sloth the size of an elephant. When his bird specimens from the Galapagos islands were examined, it was revealed that on each island there was a different species of finch, each one modified in different ways.

In this critical time during the inception and development of Darwin’s theory of evolution, Darwin began to re-evaluate his views on New Zealand and its significance to natural history.  Tied up with the evolutionary ideas that Darwin was considering was the idea that species do not stay in one place – geographical separation meant that they would experience different environmental pressures and be required to adapt in different ways.  New Zealand, with its isolation, its lack of native land mammals and its unique collection of flora and fauna provided a powerful case study in examining these ideas. In a letter to the geologist Julius Von Haast, Darwin writes:

“I really think there is hardly a point in the world so interesting with respect to geographical distribution as New Zealand”

KowhaiDrawingOne scientist whom Darwin frequently corresponded with on the topic of New Zealand was the great British botanist Joseph D. Hooker, who like Darwin had managed to gain passage on a ship and travel around the world. The pair discussed at length the distribution of Kōwhai, and how very similar species are found in Chile and across the southern hemisphere islands. A friendly rivalry struck up in which Hooker believed that this could be explained by ancient land bridges, whereas Darwin believed it was the result of dispersal by sea, wind and animals. To prove his hypothesis, Darwin performed a range of experiments with seeds, floating them in salt water and germinating them.  When Hooker was unable to supply Darwin with Kōwhai seeds to test, Darwin goaded him:

“I believe you are afraid to send me a ripe [Kōwhai] pod for fear I should float it from N. Zealand to Chile!”

New Zealand is also mentioned in many of Darwin’s letters to a host of scientific colleagues and public figures in both Europe and New Zealand. In a letter to the Governor of New Zealand George Grey, Darwin recommends that limestone deposits around the Bay of Islands be investigated for Moa bones, as New Zealand is “eminently instructive…in its lack of terrestrial (mammals).” He also requests that New Zealand scientists examine whether there is any evidence of the country being covered in glaciers, as he felt past climates might have had a large impact on its natural history.

On The Origin of Species

When it came to writing his On the Origin of Species Darwin used many examples from New Zealand to bolster his arguments. In one chapter he discusses how islands only contain a sample of the species found on nearby continents, and where a group is absent, other creatures fill the role which that group would have performed.

“Oceanic islands are sometimes deficient in certain classes, and their places are apparently occupied by the other inhabitants…in New Zealand gigantic wingless birds, take the place of mammals.”

Moa_Heinrich_Harder

He also explores how this isolation can result in greater vulnerability, as native species are not adapted to cope with species brought in by human agency. Commenting on the rapid spread of European rats and weeds in New Zealand he lays out an eerily prophetic vision for the future:

“…if all the animals and plants of Great Britain were set free in New Zealand, that in the course of time a multitude of British forms would become thoroughly naturalised there, and would exterminate many of the natives…”

Today, over 30,000 introduced plant species occur in New Zealand. Of these around 2,500 are completely naturalised in the wild and about 300 of these are major environmental pests.

Despite his initial distaste for the island, New Zealand began to assume a prominent role in Darwin’s thinking and correspondence and helped to inform parts of his evolutionary theory.  While New Zealand ultimately had an important impact on Darwin, he in turn had a monumental impact on New Zealand, changing the way scientists would view its native flora and fauna forever.

Charles Darwin in 1881

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