Thousands of years ago, humans domesticated every possible large wild mammal species fulfilling all those criteria and worth domesticating, with the result that there have been no valuable additions of domestic animals in recent times, despite the efforts of modern science.

Although native Africans domesticated some plants in the Sahel and in Ethiopia and in tropical West Africa, they acquired valuable domestic animals only later, from the north.

Humans have been evolving for millions of years longer in Africa than in Europe, and even anatomically modern Homo sapiens may have reached Europe from Africa only within the last 50,000 years. If time were a critical factor in the development of human societies, Africa should have enjoyed an enormous head start and advantage over Europe.

Science is often misrepresented as ‘the body of knowledge acquired by performing replicated controlled experiments in the laboratory.’ Actually, science is something broader: the acquisition of reliable knowledge about the world.

Measles and TB evolved from diseases of our cattle, influenza from a disease of pigs, and smallpox possibly from a disease of camels. The Americas had very few native domesticated animal species from which humans could acquire such diseases.

For better or worse we're in an age of disbelief," Rico said, "An age of science and a need for proof.