Without the Asteroid

About 65 Million years ago, an asteroid or comet 10-15 miles in diameter struck the earth in what is today the Yucatan Peninsula, forming what is called the Chicxulub crater, causing climate change and killing most plants and animals, large and small, and making extinct all large creatures, including the giant lizards we call dinosaurs.  Small creatures: small birds, small mammals, small lizards, insects, etc., managed to survive and all animal life larger than about the size of a human fist descends from the few survivors, including us humans.

If the asteroid had missed the earth, the big dinosaurs would probably still be among us. Without them, mammals were able to evolve to fill the top predator niches, but had the asteroid not killed them, they'd still be eating everything that's not good at hiding or running away.  The things that evolved into monkeys and apes would have had a much harder time competing until they grew the intelligence to turn the tables on the dinosaurs.

Were there intelligent dinosaurs?  Clearly yes.  Those surviving dinosaurs: crows and ravens, are nearly as smart as dogs and in some ways smarter.   They are more social than most other types of birds, and it seems like that ability to work together provokes the development of communication, and that feeds back into speakers ability to come up with increasingly cunning plans.  Other dinosaurs also worked together--The movie portrayal of Velociraptors is hyperbole to make a good story, but they did work in teams probably planned traps.  It's not that big a step to sitting around after dinner telling stories and making plans for the next day.  Our hands evolved from claws that are effective at climbing and catching prey to things that are better at using tools and weapons, which gave us a huge opportunity to generalize: select the right tool for the task, rather than being stuck with the one at the end of your arm.  Things like spears are essentially impossible for non tool using creatures.

Without the asteroid, a dinosaur would have evolved to fill this niche. Perhaps it would have developed the sort of awareness that we call intelligence.  It probably wouldn't have been one of the giants: a top predator has fewer evolutionary pressures than the middle sized ones.  It's easy to imagine them being bipedal (so they can specialize their hands and not need them for walking), neither too big nor too small; probably 3 to 7 feet tall, living in groups of a few families.  It's unlikely they could fly--wings use the same limbs that hands are on, which would preclude them from handling and making tools.  But they might have feathers and tails.  There's nothing particularly magic about 5 fingers, but the opposable thumb is crucial, although it might be implemented in a variety of ways.   Could have 3 fingers and two thumbs, or 6 fingers and one thumb.  But being a vertebrate, they'd have the head on top and 4 limbs, which constrains the possibilities quite a bit.

In addition the smarter birds, there are several other critters that have developed pretty high levels of intelligence.  Dolphins are pretty smart.  Groups of them will make sophisticated hunting plans.  They clearly have a relatively sophisticated language.  Their lack of hands limits them.  Of course they developed well after the K-T asteroid--their evolution would have been different had the big dinosaurs survived.   Octopuses are also pretty smart and they don't use it for teamwork.  They are capable of pretty significant manipulation with their tentacles.  And they do predate the K-T asteroid.