In Kenya's national museum, wide-eyed schoolchildren gaze at blackened skeletons of long gone ancestors, 1.5 million-year-old remains that provide key lessons today for modern teachers of mankind's origin.

For deeply religious Kenya – dubbed the "cradle of mankind" for the wealth of early hominid fossils dug up from its soil showing man's evolution – the famous remains challenge literal teachings of Christianity, Islam and traditional beliefs.

While across the world teachers must juggle science and religion, the fossils of Kenya provide stark examples found in few nations elsewhere.

"There have been challenges in teaching evolution ... largely because of the religious teachings on creation, which are deeply entrenched," said Fredrick Kyalo Manthi, head of the paleontology section at National Museums of Kenya.

Such teachings "tend to disregard the scientific explanation that all biological species, including humans, have generally evolved from simple forms to complex forms", he added.