Evolution of the horse
This image shows a representative sequence but should not be
construed to represent a "straight-line" evolution of the horse.
Reconstruction, left forefoot skeleton (third digit emphasized
yellow) and longitudinal section of molars of selected prehis-
toric horses
The evolution of the horse involves the gradual develop-
ment of the modern horse from the fox-sized, forest-
dwelling Hyracotherium. Paleozoologists have been able
to piece together a more complete picture of the mod-
ern horse’s evolutionary lineage than that of any other
animal.
The horse belongs to an order known as Perissodac-
tyla, or "odd-toed ungulates", which all share hoofed
feet and an odd number of toes on each foot, as well as
mobile upper lips and a similar tooth structure. This
means that horses share a common ancestry with tapirs
and rhinoceros. The perissodactyls originally arose in
the late Paleocene, less than 10 million years after the
Cretaceous-Tertiary extinction event. This group of an-
imals appears to have been originally specialized for life
in tropical forests, but whereas tapirs and, to some ex-
tent, rhinoceroses, retained their jungle specializations,
modern horses are adapted to life on drier land in the
much-harsher climatic conditions of the steppes. Other
species of Equus are adapted to a variety of intermediate
conditions.
The early ancestors of the modern horse walked on
several spread-out toes, an accommodation to life spent
walking on the soft, moist grounds of primeval forests.
As grass species began to appear and flourish, the
equids’ diets shifted from foliage to grasses, leading to
larger and more durable teeth. At the same time, as the
steppes began to appear, the horse’s predecessors
needed to be capable of greater speeds in order to out-
run predators. This was attained through the lengthen-
ing of limbs and the lifting of some toes from the ground
in such a way that the weight of the body was gradually
placed on one of the longest toes, the third.
History of research
Restoration of Eu