Related Experiment Video
Updated: Jul 10, 2026

High-Throughput Behavioral Aging and Lifespan Assays Using the Lifespan Machine
Published on: January 26, 2024
Line and grade in the extinct medius species group of sigmodon
Abstract:
Remains of Sigmodon minor and Sigmodon medius, extinct cotton rats comprising the medius species group, have been recovered from both Kansas and Arizona. Sigmodon minor evolved from Sigmodon medius, and the available evidence suggests that Kansas populations of Sigmodon minor were derived from Kansas populations of Sigmodon medius, while Arizona populations of Sigmodon minor were derived from Arizona populations of Sigmodon medius. This multiple origin of a single mammalian species is similar to the origin proposed by Carleton Coon for the races (subspecies) of Homo sapiens.
Related Concept Videos
Speciation Rates
Limits to Natural Selection
The Fossil Record
Notch Signaling Pathway
The Notch gene came into the limelight in 1914 after the discovery that its mutation in Drosophila melanogaster leads to a serrated (or "notched") wing margin phenotype. It was not until 1985...
Microbial Classification System
Modern Molecular Taxonomy

