This article on the BBC site intrigues me.

Some of the oldest words in English have been identified, scientists say.

Reading University researchers claim "I", "we", "two" and "three" are among the most ancient, dating back tens of thousands of years.

Their computer model analyses the rate of change of words in English and the languages that share a common heritage.

The team says it can predict which words are likely to become extinct - citing "squeeze", "guts", "stick" and "bad" as probable first casualties.

"We use a computer to fit a range of models that tell us how rapidly these words evolve," said Mark Pagel, an evolutionary biologist at the University of Reading.

"We fit a wide range, so there's a lot of computation involved; and that range then brackets what the true answer is and we can estimate the rates at which these things are replaced through time."

And later...

The researchers used the university's IBM supercomputer to track the known relations between words, in order to develop estimates of how long ago a given ancestral word diverged in two different languages.

They have integrated that into an algorithm that will produce a list of words relevant to a given date.

"You type in a date in the past or in the future and it will give you a list of words that would have changed going back in time or will change going into the future," Professor Pagel told BBC News.

"From that list you can derive a phrasebook of words you could use if you tried to show up and talk to, for example, William the Conqueror."

That is, the model provides a list of words that are unlikely to have changed from their common ancestral root by the time of William the Conqueror.

Mmm...