[jamest (OP)]

Colin with an interesting hypothetical: 'If the extinction event which killed off the dinosaurs hadn't occurred, would mankind still have risen to become the dominant species?'

[Bored chemist]

If dinosaurs hadn't gone extinct, would humanity have emerged?

Ask a chicken.

[alancalverd]

My aunt once remarked "If it wasn't for Jewish weddings, the country would be overrun with chickens."

La lutte continue!

[Halc]

If the extinction event which killed off the dinosaurs hadn't occurred, would mankind still have risen to become the dominant species?

Evolution is a chaotic system, so even if one leaf took a minute longer to fall from some tree back 75 million years ago, mankind would not ever have existed.  Everything we know would be different. Some other intelligent species may have evolved, perhaps related to an octopus, probably the next most viable candidate.

Mammals were long since around since before the extinction of the dinosaurs, so there would very much be mammals of some sort, just not the ones we see today.

[evan_au]

It is possible that evolution got locked into a dead-end, with large, fast, meat-eaters
- These preyed on heavily-armoured vegetarians at ground level
- The very large vegetarians that could eat tree leaves were probably protected by sheer bulk

There were a lot of smaller dinosaurs and mammals scurried around in the undergrowth.

If your computer locks up, reset it... 

[Petrochemicals]

I think the real question is if earths temperature had not reduced would mammals be the dominant creature type?

[Billy Fisher]

I think if the dinosaurs hadn't gone extinct, humans probably wouldn't have had the chance to rise to the top. Mammals were around before the extinction, but they were mostly small, low-profile creatures because dinosaurs dominated. It?s hard to say what would?ve happened in the long run, but I imagine something would?ve eventually created space for mammals to evolve, maybe a different kind of extinction or shift in the ecosystem. In the end, I think the dinosaurs? extinction gave mammals, including us, the opportunity to thrive in ways we wouldn?t have if they kept ruling the planet.