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December 16, 2025

Q&A: From ‘mongoose-like’ to lions, tigers and bears (oh my) — how changes in Earth’s climate shaped carnivorans

The ancestors of our furry cats and dogs once looked similar to today’s modern mongoose, a mammal with a long body and small, round ears. In fact, all members of the order Carnivora, which includes a variety of mammalian species, such as bears, wolves and even seals, evolved from these ‘mongoose-like’ creatures.

How did such a variety of body shapes emerge from one body type? New research led by the University of Washington suggests that two different climate transitions millions of years ago fueled this change.

The team, led by Chris Law, a UW principal research scientist in biology, studied the skeletal shapes of more than 850 carnivoran specimens held at 17 different natural history museums. The specimens include almost 200 different species of carnivorans: 118 that currently exist and 81 that are extinct.

The researchers found that the Eocene-Oligocene Transition, which took place around 34 million years ago, led to changes in body shape between different carnivoran families — such as between cats and dogs. Then the Mid-Miocene Climate Transition, which took place around 15 to 13 million years ago, led to changes within families — such as changes between canid species.

The team published these findings Dec. 16 in Proceedings of the Royal Society B.

UW News reached out to Law, who is also an affiliate curator at the UW Burke Museum of Natural History and Culture, to learn more about these results and what they mean for carnivorans today.

Can you talk about the significance of these results?

Chris Law: Major transitions in climate can lead to tremendous changes in biodiversity on Earth. Here, we found that climate and environmental transitions over the past 56 million years facilitated the diversification of modern carnivorans and their body forms.

Before these climate transitions, early carnivorous mammals occupied most niches as the top predators and therefore prevented the ancestors of modern carnivorans from exhibiting much body shape diversity. But climate transitions contributed to the extinction of these early carnivorous mammals, releasing the ancestors of modern carnivorans from these constraints and enabling them to exploit new environments and resources. Thus, climate transitions enabled the ancestors of modern carnivorans to increase their phenotypic diversity and fill these new niches. Our work shows how the radiation of carnivorans — and probably other animal groups — occurs in sequential evolutionary phases triggered by multiple climatic and environmental transitions.

What was happening climate-wise during the Eocene-Oligocene and the Mid-Miocene Climate transitions?

CL: The Eocene-Oligocene Transition, which lasted for about 500,000 years, was characterized by plummeting global temperatures and the appearance of the first Antarctic ice sheets. The Earth’s climate transitioned from a warm ‘greenhouse’ with relatively consistent temperatures to a cooler, temperate ‘icehouse’ with increased seasonality, all of which led to habitat transitions from warm humid forest to dry temperate forests interspersed with grasslands.

The Mid-Miocene Climate Transition, which lasted around 2 million years, can also be characterized as another major period of rapid temperature decline, increased aridity and enhanced seasonality, which in turn facilitated further trends toward grasslands from forest habitats.

Why do you think one transition led to diversification between families and the other led to diversification within families?

CL: The Eocene-Oligocene Transition was the first release point for modern carnivorans. It eliminated most competing early carnivorous mammals and allowed early modern carnivorans to exploit these novel habitats, resources and other opportunities. These led to the appearance of all modern carnivoran families from the Early Oligocene to the Mid-Miocene.

The onset of the Mid-Miocene Climate Transition created even more novel habitats and resources, giving modern carnivorans even more opportunities to further diversity and exploit the new ecological niches during the Late Miocene to the Pleistocene. And the lack of other competing carnivorous groups may have helped fuel this period of diversification. As niche space is filled to capacity, additional skeletal diversification and evolution of skeletal innovations within families may have also been necessary to help partition species that are ecologically similar to each other.

Can you give some examples of some of the mammals that reside in the order Carnivora?

CL: Modern carnivorans are very phenotypically diverse. They range from dogs and cats to small elongated weasels and robust bears. Seals, sea lions and walruses are also carnivorans even though they spend the majority of their time in water and have flippers.

Extinct pan-carnivoran groups also include animals like saber-tooth cats, hyena-like dogs and bear-dogs — dog-like animals the size of bears.

There are also some surprises: pandas, red pandas and kinkajous all belong in the carnivoran lineage even though they are not carnivorous.

Why did modern carnivorans all start out with mongoose-like body plans?

CL: As far as we know, the mongoose body plan is a very generalized body form. That is, they are not specialized to eat a specific food or move in a certain way, unlike a specialized runner like a cheetah or wolf, a specialized digger like a badger or a specialized climber like a panda. An issue with being a specialist over evolutionary time is that you may be prone to extinction if your resources or habitat change. Thus, being a generalist can be evolutionary advantageous.

So did mongooses just not change that much over time?

CL: Most likely, the mongoose — and the similarly shaped civets — retained their body types from the early carnivorans. It’s the other carnivoran groups like felids, canids and ursids that are the weird ones, because they evolved different body forms from the generalized mongoose body plan.

Do these findings have any bearing on our current understanding of these species and on our current climate situation?

CL: This study shows how major climate transitions can have profound impacts on the evolution of one group of mammals. For example, climate transitions can be detrimental to one group, leading to extinction, but can be advantageous to another group by eliminating competitors, which creates new habitats and facilitates diversification. So in the present, anthropogenic climate change may lead to the extinction of some species but we could see others take advantage of it.

Leslea Hlusko at the National Research Center on Human Evolution and Z. Jack Tseng at the University of California, Berkeley are also co-authors on this paper. This research was funded by the National Science Foundation, a University of Texas early career provost fellowship, an Arthur James Boucot research grant through the Paleontological Society, a Vertebrate Paleontology Collections Study grant through the Burke Museum and the European Research Council within the European Union’s Horizon Europe.

For more information, contact Law at cjlaw@uw.edu.

Tag(s): Burke Museum of Natural History & Culture • Chris Law • College of Arts & Sciences • Department of Biology

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