Mammalian Evolution and Paleoclimate Dynamics in North America

North American mammalian evolution has been shaped by a complex interplay between tectonic events, shifting climates and evolving ecosystems throughout the Cenozoic. Following the end-Cretaceous extinction, early ungulates and small mammals diversified rapidly under warm, greenhouse conditions. Major cooling and drying trends during the Oligocene and Miocene promoted the expansion of open grasslands and savanna-like environments, driving adaptive radiations in herbivorous clades such as camelids, equids and artiodactyls. Pleistocene glacial–interglacial cycles imposed repeated habitat fragmentation and range shifts, influencing body-size distributions, migratory patterns and the eventual extinction of megafauna.

Advances in palaeoclimate reconstruction, from geochemical proxies to machine-learning models, have clarified how atmospheric carbon dioxide, temperature and precipitation regimes controlled vegetation turnover and faunal responses. Integration of fossil-calibrated phylogenies with environmental data reveals that habitat transitions—from closed forests to open plains—mediated indirect effects of climate on body size, competitive interactions and niche partitioning. Understanding these dynamics offers insights into the resilience and vulnerability of mammalian communities in the face of ongoing anthropogenic change.

Research from Nature Portfolio

Recent studies have used physiological and climate modelling to assess future mammalian vulnerability under extreme greenhouse conditions driven by tectonic reorganisation. By projecting pCO₂ levels and solar forcing during the next supercontinent cycle, researchers evaluated heat-stress thresholds using indices of dry-bulb and wet-bulb temperatures, revealing potential tipping points beyond which mammalian thermoregulation would fail.

A data-driven approach employing Bayesian deep learning has reconstructed North American paleovegetation across the Cenozoic. By integrating fossil occurrences, geologic models and paleoclimate proxies, this work identifies the emergence of open habitats around 23 million years ago and quantifies their rapid expansion into the Quaternary, demonstrating how machine-learning techniques can extract hidden signals from complex palaeoecological data.

Mammalian Evolution and Paleoclimate Dynamics in North America publication trend

The graph below shows the total number of articles in mammalian evolution and paleoclimate dynamics in north america across all publications each year (not limited to Nature Index journals).

Technical terms

pCO₂: Partial pressure of atmospheric carbon dioxide, indicating greenhouse gas concentration.

Cenozoic: Geological era from 66 million years ago to present, during which mammals diversified after the end-Cretaceous extinction.

Neogene: Interval of the Cenozoic spanning 23–2.6 million years ago, marked by global cooling and grassland expansion.

Humidex: Combined heat and humidity index used to assess thermal stress on organisms.

Bayesian deep learning: Probabilistic modelling approach that integrates Bayesian inference with neural networks to infer patterns from complex datasets.

Artiodactyl: Even-toed ungulates, a diverse order of hoofed mammals including deer, camels and bovids.

References

1. Climate extremes likely to drive land mammal extinction during next supercontinent assembly. Nature Geoscience (2023).
2. The origin and evolution of open habitats in North America inferred by Bayesian deep learning models. Nature Communications (2022).
3. The Neogene Savannas of North America: A Retrospective Analysis on Artiodactyl Faunas. Frontiers in Earth Science (2020).
4. Mammalian body size evolution was shaped by habitat transitions as an indirect effect of climate change. Global Ecology and Biogeography (2022).
5. Why aren't rabbits and hares larger?. Evolution (2021).