Some research was done by Professor Bryan Sykes of Oxford in the late 1990's, which showed that for many surnames in Britain, (about half of them) the name originated from the name of a single ancestor. Although in some cases the name had been passed on to someone who was not a true descendant, in about half the cases, the name was passed to true descendants. This means that people who share an unusual surname are likely to be related.
The research was published in The American Journal of Human Genetics.
At time of writing, there is an entry on the BBC web site:
However such a relationship due to a shared surname may be very weak, and might mean sharing only a single ancestor out of perhaps hundreds of different ancestors. We should not forget the maternal side of the family tree. For example our grandparents would have usually 4 different surnames to whom we are related. go back another generation and it's 8, then 16 etc. You only need go back a few generations and the number of ancestors gets very big indeed.
In fact a very large proportion of the inhabitants of the British Isles are very likely to be related. It was once estimated that about half the population are descended from Henry VIII. It hasn't got a lot to do with surnames.
It is interesting to to hear people say that "We" in Britain were invaded by the Romans, or Vikings or Normans, but in fact we are likely to have been descended from those people ourselves.
I read somewhere that most great people of history were not the eldest son. (Perhaps Charles Darwin is such an example, maybe Newton and Einstein too?) There was some theory presented at the time. Well I am the eldest of three brothers, and in material things I am the least successful, but I have my own theory for it, based on my own experience. Most people's prosperity increases as they get older, at least over the period when they will be raising a family. As a result the first born experience less prosperity (or greater poverty) than their youngers. This combines with another observation, that people like to maintain a level of prosperity which they have become accustomed to. Maybe being relatively poor is not so bad and perhaps the older siblings recognise that they can be eaually happy without much prosperity. In my own case one of the big things I learnt at university was how to live off a low income, but still have an enjoyable time.
Recently, in 2008, a study by Professor Joseph Holz of Duke University, North Carolina discovered that the oldest children in a family are likely to face the toughest discipline. There seems to be truth in the belief that younger siblings get away with more. The reason Professor Holz gives is that harsher treatment of the older children acts as a deterrent to their younger siblings. The article was published in The Economic Journal. Incidentally, this theory is entirely consistent with what Richard Dawkins says in his excellent book The Selfish Gene, i.e. that parents are driven to promote their genes at all costs (and hence I deduce that this prevails over ethics and fairness).
The news of this was covered in BBC Radio 4's today programme on 16-04-08 and at the time of writing there is a link to a web page about it:
The Selfish Gene by Richard Dawkins is an amazing book. It explains all those great mysteries which have puzzled mankind since Man evolved. The origin of life on earth and the origin of mankind. But it also explains a lot about family relationships. At the most primitive level, animals wish to see the perpetuation of their genes more than anything else, and at all costs. Man is no exception. A person is 50% related to his parent, a son and a sibling, but 100% related to himself. Many family decisions are made in a way which will maximise the perpetuation of his genes, and it CAN sometimes cause conflicts. There may be decisions to make about whether one family member should be favoured over another.
It is strange that we often regard our biological urges (notably sex) to be base and low, and that seeking to fulfil those urges to be of low moral value. However when it comes to reproduction, and wanting to further the interests of our close relatives, society regards these things as entirely justified, even praiseworthy.