54. On Hyrax.

Dearly Beloved,

On 9th April Prof. Dr. Fr. Mackintosh's wrote a DB letter which focused on the hyrax. When I read it, a huge scroll of evolutionary history unwound to reveal itself in all its diversity and wonder. Proverbs 30;26 describes hyrax as “a feeble folk, yet make they their houses in the rocks.”

Early taxonomy of both animals and plants has been revolutionised by recent advances in genetic analysis which have supplemented the study of comparative anatomy and the the morphological structures revealed in fossils that has taken place in museums and similar institutions over the last two hundred years. Indeed the history is of the Afrotheria, meaning African beasts, the group to which the five species of extant hyrax belong, continues to be better understood by the year. Africa was isolated when the Afrotheria evolved so there was little competition from “alien” species.

Once upon a time (actually about, 65 million years ago) there were two small, furry animal about the size of the present day hyrax belong to a genus rejoicing under the name of Ocepeia. This name has no erudite Ancient Greek etymology but refers to the OCP the Office Chérifien des Phosphates, the Moroccan government's phosphate mining company in whose quarries the fossilised remains of these two creatures were found.

The latest research suggests that Ocepeia are the stem from which two main branches of Afrotheria derived. One comprised mostly insectivores (e.g. ardvarks  --termite and ant specialists -- golden moles, and tenrecs ) and the others herbivores – dugong, elephants, hyrax. All three of these taxa have well developed canine teeth which form tusks in elephants, male dugong and hyrax. That separates them taxonomically from rodents whose cutting teeth derive from incisors. All three taxa have flat nails rather than the claws we see in rodents although Dugong have no rear limbs at all. The Afrotheria species evolved and diversified to fill the available space and to utilise the available resources in Africa. Much convergent evolution is evident with ancestors resembling both small cattle and one, a rhinoceros (but the horn was not made of hair, like the modern rhino, but instead of bone and keratinised skin). The transition of the dugong and manatees back into marine and fresh water species is most extraordinary -- after all, it took many millions of years of evolution for animals to be able to survive on land, a demanding and dehydrating environment.

Most of the diverse Afrotheria species are now extinct and they have been replaced by modern mammals, one and two toed herbivores, insectivores and carnivores. Approximately three hundred and ninety five species of rodents are now to be found in Africa. Originally they evolved in Asia but started to enter other realms about 56.3 million years ago as land bridges were formed by continental collision and these rodents would have been devastating competitors for the hyrax and closely related species.

It is not clear why rodents have been so successful, but small size, a very short reproductive cycle, an ability to survive on a huge diversity of food, and the possession of mouth parts which reduce tooth wear are believed to be important. Rodents may have out-competed hyrax because their clawed feet help them to dig burrows for shelter which would allow them to establish themselves in the richest environments whilst perhaps the elephantine feet of the hyrax did not evolve so rapidly and usefully, so they are left to live among the rocks where rodents find burrowing difficult. So the hyrax, which lives amongst the rocks, is surely a relict species driven to a marginal, stony, habitat. A weak people indeed! Or should hyrax be celebrated instead, as great survivors?

We must be glad that the writer of Leviticus 11:5 mistook the aggressive teeth chattering of the hyrax for chewing the cud. The lawgiver believed that it chewed the cud but did not have a cloven hoof so it was unclean. Surely otherwise the hyrax, in Israel at least, would by now have been eaten to extinction like its fellow Afrotherian, Steller's sea cow a hapless relative of the Dugong, made extinct through human hunting almost as soon as it became known to science in 1741?

We humans should be impressed by the sheer number and huge diversity of species that have evolved on Earth but which have then become extinct as they competed with one another in unstable environments as the climate changed, volcanoes erupted, continents collided and meteors descended. A new extinction risk is that Homo sapiens has been so successful he pollutes his own planet, a status no other species has attained, but of which he remains largely oblivious.

Peace,

Paul.

Completed: 13th April 2021.

Photo: Paul Munton

A Wasp Feeding amongst the flowers of apple mint. Wasps are a highly evolved group of species with complex life histories.



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