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Last Word is New Scientist’s long-running series in which readers give scientific answers to each other’s questions, ranging from the minutiae of everyday life to absurd astronomical hypotheticals. To answer a question or ask a new one, email lastword@newscientist.com

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Why does water never move in straight lines? Even running down a windowpane, it wiggles. Is there any explanation for this?

Bobby Bazalgette,

Carmarthen, UK

When did hominids start to decorate their food and do any other species do the same?

Andrew Murray,

Moore, South Carolina, US

To answer this question – or ask a new one – email lastword@newscientist.com.

Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.

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