Had humans evolved and spread from Mesoamerica rather than Africa, things would be so much different. The livestock would be different as well as the domestication of the animals. On page 160, Diamond lists the major five species of big herbivorous domestic mammals and mentions that the top five are sheep, goats, cows, pigs, and horses. What I noticed was that it says that these animals were found either in West and Central Asia, Eurasia, and North Africa. These animals were and still are very important because they provide so much. For example cows produce milk, cheese, and meat and pigs can be eaten as well so as far as those animals, they are very important.
Horses were very helpful when it came to humans spreading. Humans domesticated these animals and they turned out to be very useful. It would've taken much longer for humans to spread around the world without the help of horses, mainly. The reason it would've been different had humans evolved in Mesoamerica is because horses weren't found in that area of the world. Everything would've been much slower. If humans started spreading from Mesoamerica and moved west to Eurasia and Africa, it would've been harder for them to domesticate these animals. It would've taken them much longer to begin working with crops if they didn't have domesticated animals because these animals have been proven to be very helpful with crops. For example cows provide the plants with very good fertilizer. Of course Mesoamerica had animals of their own such as llamas and alpacas but even then, it would take longer for them to spread. Humans who evolved in Africa, of course, had a difficult time at first with getting food since almost half of Africa is dessert, but once they stumbled upon the Fertile Crescent, they were good to go. With all this being said, one can only say that had Mesoamerica been the new Africa, the whole spreading around the world process would've been slower, animal domestication would've been more difficult, and it would've taken longer for societies to develop.