# why did the dinosaurs not evolve back **URL:** \ **Category:** Factual Questions\ **Created:** [August 13, 2013, 3:34pm UTC](https://boards.straightdope.com/t/why-did-the-dinosaurs-not-evolve-back/666138 "2013-08-13T15:34:17Z")\ **Posts on this page:** 7\ **Page:** 6
**Author:** ![Nava](https://avatars.discourse-cdn.com/v4/letter/n/da6949/32.png) [@Nava](https://boards.straightdope.com/u/Nava)\ **Post date:** [January 10, 2018, 1:09pm UTC](https://boards.straightdope.com/t/why-did-the-dinosaurs-not-evolve-back/666138/101 "2018-01-10T13:09:57Z")
> [@Mangetout](#): > > If zombie evolution is real, why aren’t there any dinosaur zombies!? Lack of CGI budget. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [January 10, 2018, 2:04pm UTC](https://boards.straightdope.com/t/why-did-the-dinosaurs-not-evolve-back/666138/102 "2018-01-10T14:04:29Z")
Lack of CGI budgies. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 10, 2018, 2:18pm UTC](https://boards.straightdope.com/t/why-did-the-dinosaurs-not-evolve-back/666138/103 "2018-01-10T14:18:20Z")
Lack of Harry Dresden. ---
**Author:** ![Gyrate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gyrate/32/3588_2.png) [@Gyrate](https://boards.straightdope.com/u/Gyrate)\ **Post date:** [January 10, 2018, 3:05pm UTC](https://boards.straightdope.com/t/why-did-the-dinosaurs-not-evolve-back/666138/104 "2018-01-10T15:05:26Z")
> [@Colibri](#): > > No it wasn’t. No dinosaur was as small as many modern mammals. Even if you include birds as dinosaurs, the average size of non-avian dinosaurs was far larger than most modern birds. I know this is an old post but I’m confused by “No dinosaur was as small as many modern mammals.” There were certainly small dinosaurs - velociraptors were about the size of a medium-sized dog (Jurassic Park be damned - the raptors in the film are much closer to a Deinonychus than a Velociraptor) and your basic Compsognathus was roughly chicken-sized. The average dino size may have been much bigger than the average modern mammal size, but there were small dinos around too. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [January 10, 2018, 3:29pm UTC](https://boards.straightdope.com/t/why-did-the-dinosaurs-not-evolve-back/666138/105 "2018-01-10T15:29:08Z")
> [@Gyrate](#): > > I know this is an old post but I’m confused by “No dinosaur was as small as many modern mammals.” There were certainly small dinosaurs - velociraptors were about the size of a medium-sized dog (Jurassic Park be damned - the raptors in the film are much closer to a Deinonychus than a Velociraptor) and your basic Compsognathus was roughly chicken-sized. > > The average dino size may have been much bigger than the average modern mammal size, but there were small dinos around too. Think mice and shrews and the smaller bats. Most mammal species are either rodents or bats. There are large rodents and bats, but many are quite small. ---
**Author:** ![Morgenstern](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@Morgenstern](https://boards.straightdope.com/u/Morgenstern)\ **Post date:** [January 10, 2018, 3:33pm UTC](https://boards.straightdope.com/t/why-did-the-dinosaurs-not-evolve-back/666138/106 "2018-01-10T15:33:39Z")
> [@breakneck](#): > > well what about girafes? why do they have long necks and so tall? … They have genes. Levis I think. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 10, 2018, 3:45pm UTC](https://boards.straightdope.com/t/why-did-the-dinosaurs-not-evolve-back/666138/107 "2018-01-10T15:45:56Z")
> [@breakneck](#): > > well what about girafes? why do they have long necks and so tall? Anyways i was not talking about mammals and how they evolved i was talking about how dinosaurs evolved . Then they are wiped out with a mass extinction . Why did they not evolve again . Like they did the first time around? **Moderator Note** These questions were answered the first time this thread was active. I don’t see any point in just asking the exact same question over again when the question has been answered. This is closed. Colibri General Questions Moderator > [@Gyrate](#): > > I know this is an old post but I’m confused by “No dinosaur was as small as many modern mammals.” There were certainly small dinosaurs - velociraptors were about the size of a medium-sized dog (Jurassic Park be damned - the raptors in the film are much closer to a Deinonychus than a Velociraptor) and your basic Compsognathus was roughly chicken-sized. > > The average dino size may have been much bigger than the average modern mammal size, but there were small dinos around too. **John Mace** has already answered this but since it was addressed to me I will reiterate. As I said, even small non-avian dinosaurs like _Compsognathus_ were much larger than the average modern mammal. There are about 5,400 species of modern mammal, of which 1,500 are rodents, 1,200 are bats, and 400+ are shrews (together almost 60% of all mammals), the majority of which weigh less than an ounce. The median mammal weighs much less than a pound. If anyone has specific questions related to this thread feel free to open a new thread in GQ. [Previous page](https://boards.straightdope.com/t/why-did-the-dinosaurs-not-evolve-back/666138.md?page=5)