1 八上阅20 Have you ever seen a horse with toes (脚趾)
Millions of years ago, horses had many toes
They had four toes on each front foot
They had three toes on each back foot
These small horses lived in the forests
But toes helped them run over the soft, wet ground
It was once very hot in the forests
But the weather changed later
It became cold
Many trees could not live in such weather, so they died and fell down
Open fields took the place of forests
The sun made the ground dry and hard
Horses began to get bigger with climate (气候) changing
On the dry, hard land, horses needed only their middle toes for running
Their middle toes became hard
After a long time, horses had only one hard toe on each foot
We call it “hoof”
Long ago, the horse had four toes on each ________