From William Bains
Your article on the evolution of warm-bloodedness as a means to avoid fungal infection ends with speculation that global warming might drive the evolution of more warm-tolerant fungi, and lead to a raised risk of fungal pathogens in both mammals and birds (3 December, p 50).
This ignores what the rest of the article says. Fungi have had a tempting, warm environment to adapt to for hundreds of millions of years – the insides of mammals and birds – and they have not been able to do it. This suggests a more basic limitation in the biology of fungi that stops their adaptation. Increasing the number of warm places for fungi to grow is unlikely to overcome this limitation, whatever it is.
Cambridge, UK
