# Article2

By [Untitled](https://paragraph.com/@0xcf7fabb84624e743edadf280fb7d4ac27819a43b) · 2024-03-17

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For some mammals, physical differences in size do vary depending on competition for mates and the differences in how mothers and fathers invest time and energy in their offspring. Male [lions](https://www.popsci.com/story/animals/wild-lives-lion-king/) and [baboons](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4423909/) typically engage in [physical competition for mates](https://www.popsci.com/environment/trilobites-sexual-selection-trident/) and the males are larger than the females. It has been assumed that [sexual dimorphism](https://www.sciencedirect.com/science/article/abs/pii/B9780128043271002260#:~:text=Sexual%20dimorphism%20means%20that%20the,highly%20variable%20among%20marine%20mammals.)–where the sexes differ in size–is most common in animals. Additionally, the idea that males of a species are always larger, which is the case in lions, applies to most species has also stuck around for decades.

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*Originally published on [Untitled](https://paragraph.com/@0xcf7fabb84624e743edadf280fb7d4ac27819a43b/article2)*