Within 30,000 years, 98% of the already vanishingly small quantities of carbon-14 in bone is gone.And carbon-14 molecules from surrounding soil start to seep into the fossils.“We know that it is older than Christendom,” he wrote, “but whether by a couple of years or a couple of centuries or even by more than a millennium, we can do no more than guess.” The fog began to lift in the middle of the twentieth century, when US chemist Willard Libby and his colleagues showed that all formerly living things bear a clock powered by radioactive carbon-14.
It might even explain why humans survived and Neanderthals did not.
“I admire him,” says Paul Mellars, an archaeologist from the University of Cambridge, UK, and an expert on this period in Europe, for “the sheer doggedness and sense of vision” he has for improving radiocarbon dating of the Palaeolithic.
If you Google 'archaeologist' and 'Higham', the first hit is likely to be Charles Higham, a 72-year-old professor who has charted the origins of agriculture and government in southeast Asia.
Tom was born in Cambridge, where his father was based until 1966.
Charles then moved the family and nine-month-old Tom to New Zealand's rugged south island to start an archaeology department at the University of Otago in Dunedin.
As a teenager, Tom spent summers at Ban Na Di, a study site in northeastern Thailand, where his duties included helping with human excavations and brewing tea for the crew.
Beside a slab of trilobites, in a quiet corner of Britain's Oxford University Museum of Natural History, lies a collection of ochre-tinted human bones known as the Red Lady of Paviland.
In 1823, palaeontologist William Buckland painstakingly removed the fossils from a cave in Wales, and discovered ivory rods, shell beads and other ornaments in the vicinity.
Libby earned the 1960 Nobel Prize in Chemistry for his work.
The clock gets less accurate as the samples age, however; cruelly, it begins to fail at one of the most interesting times of human history in Europe.
Tom didn't originally plan to follow his father's path.