Mammals inherit the Earth
An explosion of diversity fills the gap the dinosaurs left
Quick facts
- Trigger
- The extinction of the non-bird dinosaurs, 66 million years ago
- Speed
- Earliest ancestors of living mammal groups within a few hundred thousand years
- Method
- 3D scans of 322 mammal skull specimens, over 20 museum collections
- Since then
- The pace of mammal evolution has slowed steadily
What happened
Mammals had existed alongside dinosaurs for most of the Mesozoic, but stayed small and constrained the whole time. That changed the moment the non-bird dinosaurs vanished 66 million years ago. Using 3D scans of 322 mammal skull specimens from more than 20 international museum collections, researchers led by Professor Anjali Goswami at the Natural History Museum traced what happened next: an explosion of diversity among placental mammals immediately after the extinction, with the earliest ancestors of today's living mammal groups appearing in the fossil record within a few hundred thousand years of the impact. The study also found that this initial burst of evolutionary speed was never matched again, slowing steadily in the tens of millions of years that followed.
Why it matters
This is the direct sequel to the asteroid impact: the empty world it left behind is what allowed the mammal lineage, including the one that eventually produced primates and us, to diversify at a pace it had never managed while dinosaurs dominated. The age of dinosaurs ends here, and the age that leads to humans begins.
How we know
The Natural History Museum's press release on Professor Goswami's research describes the 322-specimen 3D-scan study, states the rapid post-extinction diversification and its timing within a few hundred thousand years of the 66-million-year-old mass extinction, and reports the finding that the pace of evolution has slowed ever since that initial burst.
Sources
- Eutherians experienced elevated evolutionary rates in the immediate aftermath of the Cretaceous-Palaeogene mass extinction (BMC Evolutionary Biology, 2016, via PubMed Central) (2016) · Peer-reviewed (author-declared)pmc.ncbi.nlm.nih.gov · Cited as a "journal" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
- Natural History Museum, London. Social mammals evolve faster than solitary ones, according to a new study of mammal evolution (Natural History Museum press release) (2024) · Reputable sourcenhm.ac.uk · The domain "nhm.ac.uk" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
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Part of a timelineAge of Dinosaurs21 events · The age of the dinosaurs across the Mesozoic Era, from the Great Dying that cleared the way to the asteroid that ended their reign.View all →