Equus
Pliohippus
Merychippus
Mesohippus
Hyracotherium
1 million
years ago
10 million
years ago
30 million
years ago
40 million
years ago
60 million
years ago
1.6m
1.0m
1.0m
0.6m
0.4m
Single hoof,
runs quickly
over hard
ground
Other toes
lost as only
middle hoof
used
Middle toe
developed
into a
hoof, to
run faster
Toe lost for
moving
faster
over dry
ground
4 toed hoof, well
spread for
walking
on soft
ground
What is a fossil?
Fossils are evidence of a plant
or animal that lived many years
ago – skeletons, shells,
footprints
How can we use fossils as
evidence of evolution?
•
•
•
We can tell the age of many of
the layers of rock containing
fossils – this means we know
how old the fossil are
Similarities and differences
between fossils in rocks of
different ages allow us to see
how species have
evolved/changed over billions of
years
Can suggest what a habitat was
like millions of years ago
Problems with fossil evidence:
•
Few organisms form fossils
•
Fossils can be damaged by
geological activity
•
There are often gaps in
fossil records
Fossil evidence
Example: Evolution of the horse
How do we know that the horse has
evolved over 60 million years?
Fossil evidence
What changes can we tell from the
fossil records?
•
Four toed hoof has evolved into a
single hoof which is more suitable
for running
•
Modern day horse is much taller
than its original ancestor
Fossil evidence timeline
Million years ago
Fossil found
50
Monkeys and apes
200
Mammals
300
Reptiles
350
Amphibians
450
Land plants
3000
Simple bacteria