Interspecies hybrids: natural & artificial

[peter]

TIGER EVOLUTION

It would have made sense when tigers would have evolved in the last millenium or so, Siegfried. However. We know they didn't. Tigers evolved more than two million years ago and spread to different parts of southern Asia from southern China. Then the Toba erupted. The blast must have been tremendous.

Based on what I read, my guess is the intensity of sunlight could have been affected to a degree. Same, perhaps, for oxygen levels. All living organisms would have suffered. Scientists found population bottlenecks in many species and most of these could be traced back to a period just after the Toba super eruption (70 000 - 100 000 years ago). Also remember the eruption happened at the end of the Pleistocene, when many parts of Asia were covered with ice. Most species who survived seem to be tolerant of cold and my guess is this could be the reason.

In the last stages of the Pleistocene, many species recovered. Tigers again spread to the southeast of Asia to colonize Palawan, Borneo and many other parts of what was then the Sunda Shelf. When the ice melted, the Sunda Shelf was inundated and many species again became isolated. Tigers survived on Bali, Java and Sumatra until very recently. I agree they became extinct as a result of human intervention on Bali and Java, but that wasn't the reason they were different from other subspecies.

When the Sunda Shelf was inundated just before the Holocene, mainland Asia tigers spread from China to the southwest and the west. Indian tigers (Panthera tigris tigris) are distinctly different from other subspecies. The other subspecies spread in the Holocene and replaced the Chinese tiger.

One question is if they reached Manchuria and Korea before the Caspian. Another is if they reached the Caspian by crossing the western part of the Himalayas or by going west from northern China. My guess is it wasn't either-or, but and-and. Caspian tigers showed two distinct types, with those in the southwest and west smaller than those in the eastern part of Iran and Kazachstan. When they started struggling in the west, tigers from northern China and Manchuria might have started their move west. This would explain the similarity between the last Caspian and Amur tigers. Most researchers, however, think Caspian tigers spread east, towards eastern Russia.

Anyhow. There's, I think, no question tiger subspecies evolved well before humans took over. First, there is the difference between mainland Asia and Indonesia. Fysical isolation would have resulted in significant differences between both. We also have to take climate, elevation and vegetation into consideration. We could talk about the results for mammals and we could debate the status of the subspecies proposed by Pocock in 1929, but there's no question tigers inhabited very different regions in Asia and it would have shown in morphology, coat, skull and behaviour. Maybe it was a cline after all and maybe it wasn't. I think there were distinct local types, but I also think there was gene exchange. Tigers, like most mammals, are great walkers. 


FUTURE

The trick is gene exchange. It happened until it was halted by the inventions of Mr. Colt, Mr. Mauser, Mr. Winchester and Mr. Kalashnikov. Today, as a result of unchecked capitalism and the collapse of states, more and more humans have access to weapons way more sophisticated than those in use a century ago. The only thing lacking is a nice excuse to use them on a scale that would result in total chaos and my guess is we are not that far away. If it happens, it will have three major results.

One is new states and no constitutions, two is giant cities and three is depopulation of rural regions and the collapse of agriculture. As a result of a lack of organisation, we might see something that will dwarf the achievement of even the most sophisticated mosquitos. 

If they are able to weather the storm for a few more decades, tigers still might stand a chance.  Reply