Size

Bronze Age

Mostly Wagon age

  • The earlier ones could provide milk and probably pull wagons. These are what the IEs had when they conquered Europe.
  • Scientific studies show that horses were kept for their milk ~3500 to 3000 BCE, widely accepted as indicating domestication. SA2023

Early riding evidence

“five Yamnaya individuals well-dated to 3021 to 2501 calibrated BCE from kurgans in Romania, Bulgaria, and Hungary, displaying changes in bone morphology and distinct pathologies associated with horseback riding.” SA2023

Calmer stronger horse

Unlike early semi-domesticated horses, fully domesticated (taking over between 4200 and 3000 years ago) ones had only two gene changes: ZFPM1 (anxiety and aggression) and GSDMC (associated with chronic back pain in humans). SCI

The fully domesticated ones were calm enough to train to pull a chariot, and a back strong enough to ride.

क्व१॒॑ वो ऽश्वाः॒, क्वा॒३॒॑भीश॑वः +++(=रश्मयः)+++
क॒थं शे॑क+++(←शक्)+++, क॒था य॑य ।
पृ॒ष्ठे सदो॑+++(→आसनम्)+++, +++(अश्व-)+++न॒सोर् यमः॑ ॥
RV 5.61.2

Charriot age

  • Horses were mostly too small to be able to carry people on their backs (except light frail people).
  • Kikkuli the Mittani wrote a manual for horse conditioning.
  • Hence charriots - oft with multiple steeds drawing them.
  • Even charriots were small.

Iron age

  • By 800 BCE, there are more references of horse riders.
  • Back strength of the horse had increased.
  • Riders wore light armors.
  • Size remained small, legs dangled below the horse belly.

1200 Jump

  • Sudden increase in horse size between 1100 and 1250. Legs no longer dangle down.
  • Started in Central Asia, spread west fast.

Evolution

North America saw in the Eocene epoch (56-44 million years ago) a dwarf horse like animal with arched back. From that across the ages, they grew larger in size, had longer legs & bigger brains.

By the end of Pleistocene epoch (11,700 years ago), horses had spread all over the world including Eurasia via the Bering land bridge which connects Americas to Eurasia. After this land bridge was submerged, in the next 2000 years, horses went extinct in the Americas. This extinction was partly due to climate change & partly due to overhunting by humans who had just crossed over to Americas before the land bridge was submerged. This extinction was bad for American humans too as they lost the advantage of fast travel which the Eurasians had.

Back in Eurasia in Middle East & Steppes around the 5th millennium BC, humans domesticated wild horses and used them for transport & it proved out to be a gamechanger for humans as this accelerated the spread of humans, resources & even ideas.

When European colonizers finally reached the Americas in 16th century, they brought with them horses. Some of them over the next 3 centuries escaped from human captivity & gradually spread all over Americas. This is how horses which originated in Americas finally went back home.