At the risk of triggering debate on evolution, scientific understanding on these topics is in a state of considerable flux. Ideas I was taught years ago have been overturned or modified. They used to believe that the evolution of man was a linear thing, from one species if primitive man to the next. They now believe that a number of these hominids were co-existing, possible interbreeding, but some died out and were dead ends.
Same with other species - ideas change. When I was at uni I wrote a major thesis on the history of domestication. Much of what was considered the view at the time was that domestic dogs evolved with selective breeding after an early connection between man and wolf, in Europe. It now appears that multiple connections were made between a number of different species of canid, and whichever variety/tribe of man was in the area at the time (Homo sapiens by then). All dogs would have common ancestors, but they have diverged and where land bridges sank, further divergence would have occurred in isolation. It's a fascinating topic (for me). So - multiple canid species with varying characteristics depending on the area they live, but with a common, probably vulpine, ancestor. The earliest connections between dog and man is still believed to have been in hunter-gatherer society especially in the days when there were giant mammals in the world. It would take a lot of effort for a man or even a group of men to drag home an entire Irish Elk or Woolly Mammoth, so they would have butchered the meat where it fell, piled the best bits in the hide (which had the foot bones still attached for easier dragging home) then left the rest. Packs of dogs would have soon learned to associate the sound of men hunting, with the chance of a feed when the men left. It would have taken little more for packs of dogs to begin speeding up the process by driving the prey to the hunters. They have found in caves, lots of foot bones of various animals, but not a lot of the rest of these animals. It's called the "schlepp" effect, from the German word schleppen, to drag. At least, that is what we were taught about it.
Interestingly on genetic divergence and natural selection, we observed it in action while we were away in the last couple of weeks. The introduced pest, Bufo marinus (cane toad) is on the move south. I used to handle these creatures in my job years ago; they were collected in north Queensland and trucked down to Sydney. The ones we had were grey (a sort of khaki colour), warty and stubby. But we went out catching cane toads in the gardens of the place we were staying in south of the Queensland border, and while they were clearly cane toads, they had longer legs and were a rusty brown in colour, exactly the same colour as the soil. Since people are actively trying to kill them when they find them, it stands to reason that the toads with best camouflage blend in to survive, while their khaki siblings get golf-clubbed back into Queensland. Also, they have found similarly in the toads reaching Kakadu (sadly - and a lot of Aussie mammals are dying out because of it) that the toads in the advance areas have longer legs. I also noted that these toads seemed a lot more cunning when it came to evading capture, than the blobs I used to handle. Again - the smart ones survive to pass their characteristics onto their offspring.
I hate toads... and managed to despatch almost a hundred while we were away. I put them in a bag and put them in a freezer. It's a more pleasant death for them, than their victims.
Marg
