A botanist whose studies of human coprolite analysis regarded as essential in our understanding of ancient life and human origins.
When Eric Ottleben Callen died in 1970, he was living in Peru and working on the coprolites - dried or fossilized piece of animal or human excrement - found at the site of Pikimachay, an archaeological site in the Ayacucho Valley. However, he was working with some frustration.
Perhaps because of the subject matter, most scientists at the time thought that coprolite research was not useful, and Dr Callen endured some ridicule and derision. It was a hard sell to his peers at McGill University in Montreal and left him open to being the butt of predictable jokes. But he persevered.
Dr Callen discovered that dried human coprolites, typically less than 10,000 years old, can be returned to their original texture, odour, and "freshness" by a technique developed by him in 1955. He soaked the coprolite for 48 hours in a 0.5% solution of trisodium phosphate.
Today, human DNA can be extracted from coprolites, and can give a picture of what people were like and what life was like up to 90,000 years ago. Scientists can even tell when our ancestors began to speak by looking for the FOXP2 gene in the DNA. When the presence of the FOXP2 gene is detected, it means that the person was capable of the jaw movements required for speech.
Dr Callen has become something of a pioneer, and his techinique has been used in recent studies on the lives of ice age mammals, what Neanderthals ate and the diseases that ravaged early humans.
Eric Ottleben Callen received his PhD in botany while in Scotland at the University of Edinburgh. He was an unlikely person to become the “father” of coprolite analysis. After spending his professional career as a professor of plant pathology at McGill University in Canada where he researched cereal pathogens. He died before knowing the true extent of the impact his research would have, but his legacy has been a greater understanding of the origins of life.