As Darwin read Personal Narrative, he highlighted many of these examples.6 Why was it, Humboldt had asked, that the birds in India were less colourful than those in South America, or why was the tiger only found in Asia? Why were the great crocodiles so plentiful in the Lower Orinoco but absent from the Upper Orinoco? Darwin was fascinated by these examples and often added his own comments in the margins of his copy of Personal Narrative: ‘like Patagonia’, ‘in Paraguay’, ‘like Guanaco’ or sometimes just an affirmative ‘yes’ or ‘!’.
