Why blood really is thicker than water?

Have you ever thought that?

The reasons are here.

Keep your eyes!!

UNTIL about a century ago, the old Gaelic naming tradition still applied widely in Scotland. By these rules, the first son was named after his paternal grandfather, the second after his father, the third after a father's brother, with the equivalent rules on the maternal side applying to daughters.

I actually owe my first name to a revolt on the part of my mother who refused to have yet another George in the family - otherwise, if my father had had his way, I was about to be the fifth George Dunbar in a row.

But why should naming have followed these kinds of rules?

One obvious answer is that bearing the same name identifies family membership. This much is self-evident from the way we use surnames. And some surnames are clearly considerably better for this than others. While Bakers and Smiths must sadly conclude that they are unlikely to be related to strangers bearing the same name, the many variants on Gaelic family names do provide clear indications of common ancestry, partly because of their many variants.

Many name lineages are of quite modest size, and many had quite localised origins. The seaport up the road from Edinburgh notwithstanding, Dunbar is a Moray name and was rare elsewhere. A mere 16,000 or so people have held this name in the three centuries since birth (mainly baptismal) registrations became common.

Studies of parish registers from the Krummhörn area in northwest Germany show that children who survived the first year of life had more Christian names than those who did not: since names were conferred when the child was baptised on its eighth day of life, this suggests that parents already knew who would survive and who not, and hence for which children it was worth making the effort of soliciting godparents.

This sense of implied kinship even seems to persist today. This was put to direct test in a recent study carried out by evolutionary psychologists from Canada's McMaster University. They used the US census to select a set of common and rare English surnames and first names, and then e-mailed nearly 3,000 Hotmail accounts with different combinations of these names asking for help with a project on local sports team mascots, ostensibly from someone with the same or different combination of names. The test was whether the recipients took the trouble of replying. Just 2 per cent of recipients replied when they shared neither first nor surnames, but 12 per cent did so when they shared both. Shared surnames (6 per cent replies) did better than just shared first names (4 per cent of replies).

But when the names were rare in the population at large, reply rates soared to 27 and 13 per cent, respectively, when sender and recipient shared both names or just their surname. As many as a third of those replying when rare names were shared commented on the coincidence, often asking about family origins.

I recognise these response patterns in my own behaviour. Finding someone with the surname Dunbar invariably arouses my interest. But I am only mildly excited when I come across a MacDonald - surely the commonest of all Scottish surnames - even though it has been a middle name for several generations in my lineage.

Evolutionary biologists have long understood the significance of kinship (shared descent from a common ancestor) in animal and human biology. The essence of this is summed up in what has become known as Hamilton's Rule, one of the cornerstones of modern evolutionary biology named after the late WD Hamilton. While a PhD student in the 1960s, he pointed out that two individuals have a common genetic interest in each other that is proportional to the likelihood of their sharing a given gene by descent from a common ancestor, and hence that, when all else is equal, they should be more likely to behave altruistically towards each other than less closely related individuals.

Blood, as the saying goes, is thicker than water. It is a finding demonstrated by observation and experiment in organisms ranging from tadpoles to humans. Naming patterns seem to capitalise on this. In fact, the biological intuition of relatedness seems to be so strong that, in the absence of anything else, shared names can trigger sentiments of kinship even where none actually exists.

by ROBIN DUNBAR