Electronic Precinct - February 1999

Little Foot

Professor John Shaw with part of the 300 million-year-old fossil.

The Geomagnetism Laboratory in the Department of Earth Sciences played a key role in dating the hominid skeleton discovered at Serkfontein, near Johannesburg, and announced to the world in December 1999 as 'Little Foot', the oldest hominid skeleton yet discovered.

The skeleton, of one of humanity's early ancestors, was dated at about 3.5 million years by Dr David Heslop and Professor John Shaw. It is older than the 3.2 million year old Lucy, fragments of which were found in Ethiopia in 1974, and because it is almost complete will answer many of the question s concerning human evolution from ape to human.

The discovery was made by Dr Ron Clarke of the Paleo-Anthropology Research Group at the University of Witwatersrand, Johannesburg. The location was the Silverberg Grotto, within the Serkfontein Cave, near Johannesburg. Careful scrutiny revealed that the skeleton was sandwiched between layers of flowstone or stalagmite. Thes e were carefully sampled by Tim Partridge of the Climatology Research Group at Witwatersrand and, in November, precisely orientated blocks were flown to Liverpool for analysis.

In the Geomagnetism Laboratory David Heslop and John Shaw were able to calculate the age of the blocks by reference to the changes in the Earth's magnetic polarity during the time when the flowstone was deposited.

Professor Shaw explained: "The timing and duration of past changes in the Earth's magnetic field are known with great accuracy for the past 118 million years. However, to place a local sequence of changes (such as in the Silverberg Grotto) within the complete record requires that broad upper and lower age limits be set from other evidence.

'Antelope remains, which palaeontologists know to have existed in East Africa between about 2.5 and 2.7 million years ago, had been found above the skeleton and provided an upper limit. The lower limit of about 4.0 million years was assumed from the oldest (rather fragmentary) hominid remains yet found in East Africa.

'Given these restraints, the correlation of evidence from the flowstone layers above and below the skeleton to the global paleaomagnetic timescale appears to be quite clear: the hominid remains are positioned between the Gauss - Gibert reversal boundary and the termination of the Mammoth event. On this basis, the speciman can be assigned a palaeomagnetic age of between 3,220 and 3,580 million years, which means that this is the oldest hominid sleleton yet discovered anywhere in the world'.