2026-07-30 カリフォルニア大学バークレー校（UCB）
Ground sloths, which could reach the size of small elephants, originated in South America and spread into North America via the Panamanian land bridge. Courtesy of Natural History Museum of Los Angeles County
＜関連情報＞
- https://news.berkeley.edu/2026/07/30/north-and-south-america-werent-always-connected-but-their-mammals-still-found-a-way-to-intermingle/
- https://www.science.org/doi/10.1126/science.aef2893
1000万年にわたる生物地理学的待機期間が、大アメリカ生物交換の準備を整えた A 10-million-year biogeographic holding pen primed the Great American Biotic Interchange
Z. Jack Tseng, Leah X. Kahn, Adolfo Pacheco-Castro, Oscar Carranza-Castañeda, […] , and Xiaoming Wang
Science Published:30 Jul 2026
DOI:https://doi.org/10.1126/science.aef2893
Abstract
The movement of taxa between North and South America across the Panamanian land bridge, known as the Great American Biotic Interchange (GABI), established modern-day mammal assemblages in the Americas, heralding the decisive end of what has been called the “splendid isolation” of the South American fauna. Lacking substantive low-latitude records, previous work on this pattern relied on South American and temperate North American fossils to conclude that pulsed interchanges began about 2.8 million years ago (mya). Based on new low-latitude fossil data from México, we found evidence for a prolonged, triphasic interchange. Phase 1 consisted of the initial accumulation of northern higher-latitude mammals in a Mexican “holding pen” beginning 10 mya. Dispersal began in phase 2, with a strong north-south gradient and increasing biogeographic connections (7 to 3 mya). The final phase consisted of the already well-described taxonomic pulses (from ~2.8 mya).
