Elephants trade a long jaw for a trunk
What happened
Early proboscideans, the elephant lineage, fed for millions of years using a long, shovel-like lower jaw rather than a dedicated trunk. A 2024 study of Miocene proboscidean skulls found that as grasslands spread and opened up new habitat, different lineages split into different feeding strategies: Platybelodon kept a shortened lower jaw paired with a strong, flexible trunk suited to cutting plants that grew upright, while Choerolophodon specialized instead in cropping low, horizontally spreading vegetation. Across the elephant lineage as a whole, the study found that the trunk gradually took over feeding entirely, and the long mandible early proboscideans had relied on disappeared.
Why it matters
The trunk's takeover let elephant ancestors follow the same spreading grasslands that were reshaping horses at the same time, but by inventing an entirely different tool: a single flexible, grasping organ instead of faster legs and tougher teeth. It is the innovation modern elephants, the largest living land animals, still depend on for almost everything they do.
How we know
Researchers compared skull and jaw shape across multiple Miocene proboscidean genera, correlating the shrinking mandible and changing muscle-attachment points directly with each species' inferred feeding style and habitat, linking the anatomical shift to the same grassland expansion documented independently in the horse fossil record.
Sources
- Wang et al.. The trunk replaces the longer mandible as the main feeding organ in elephant evolution (2024) · 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)
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Related timelines
- Human Evolution → · The grassland world this timeline builds is the one early hominins stood up in next