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From From Malcolm Moore, Rotorua, New Zealand When it comes to the rise of burial practices, the basic needs for species are survival and reproduction. That means food, shelter and security. Dead bodies attract scavengers. For a vulnerable hominin species like Homo naledi who, for a period at least, stayed in one place, decaying bodies …

Seems to me that the custom of burial would have been more practical than anything else. After all, dead bodies lying about would have smelled pretty bad after a while and attracted wildlife.

I find the claims of species de-extinction by Colossal Biosciences unconvincing, its reasons for doing it unclear for the species it is trying to resurrect, and the prospect of the development of artificial wombs a potential horror story( 19 July, p 32 ).

Charlie Wartnaby, Cambridge, UK So I missed my opportunity to play geologist by "discovering" the weird anthropoclastic rock formed from industrial waste on the beach near Workington, Cumbria, UK. It seemed like an impossible kind of volcanic sandstone when we found the same thing on the north side of the town. It did indeed feel …

Your article on how to think about the weak and strong anthropic principles (AP) took the Barrow and Tipler formulations. These conflict with the original Brandon Carter definitions, make much less sense and haven't enjoyed much peer acceptance( 28 June, p 32 ). Carter's weak AP is that within a universe capable of supporting intelligent …

Above its "entropy catastrophe" temperature, a solid has higher entropy than its liquid, so melting would break the second law of thermodynamics ( 2 August, p 16 ). The pineal gland secretes melatonin ( 2 August, p 30 ).

I look at de-extinction this way: people interested in wildlife regret extinctions, especially human-caused ones. They would like to atone. Attempts have already been made to produce, for example, aurochs-like cattle just by selective breeding. If de-extinction results in creatures that resemble extinct species and can live and thrive in the present, there is no …

What are people going to do with animals that are de-extincted? They obviously aren't going to dump such valuable specimens in wild, unbounded habitats. No, they will be confined, possibly in a zoo, where they will be gawped at – sorry, marvelled at – by endless streams of humans. They will be poked, prodded, measured …

1 × 10 90 seems very small compared with the useful numbers used to generate cryptography keys. Given that such numbers are routinely involved in calculations with practical real-world applications, physical reality is no constraint to going full steam ahead further towards infinity.

While I am aware that breastfeeding has many benefits, as highlighted in your story, I am a living testament to the alternative. I was entirely bottle-fed as a baby, my mother having had quite enough after feeding my three siblings, especially in the climate in Singapore where I was weaned. Sixty years on, I am …