Horse

• It sleeps standing up thanks to the stay apparatus of its limbs, a system of tendons and ligaments that locks the joints with no muscular effort; it lies down only for deep sleep.
• It cannot vomit: the cardiac sphincter is so strong that it prevents reflux, which is what makes colic so serious.
• Its origin was settled in 2021, after decades of debate. Analysis of 273 ancient genomes placed the ancestors of all today's domestic horses on the steppes of western Eurasia, in the lower basins of the Volga and the Don, about 4,200 years ago.
• The Botai horses of Kazakhstan, which show bit wear from 5,500 years ago and were considered the first domestic horses, turned out not to be ancestors of modern ones: they are relatives of Przewalski's horse.
• From 2000 BC that new lineage spread across Eurasia within a few centuries and replaced almost all the others, coinciding with the appearance of the spoke-wheeled chariot of the Sintashta culture.
• Selection concentrated on two genes, GSDMC and ZFPM1, linked to back strength and temperament: more docile horses with a better back — in other words, easier to ride.
• The tarpan and Przewalski's horse do not descend from the same ancestral population as the domestic horse.

Skeleton type

Vertebrate - internal bony skeleton (mammal)

Habitat and environment

Grassland, steppe and prairie; today tied to livestock holdings worldwide

Sexual maturity

2.5 years

Gestation / incubation

11.1 months

Litter / clutch size

1

Life expectancy in captivity

35

Sources consulted: https://es.wikipedia.org/wiki/Equus_ferus_caballus