Over half a billion years ago life on earth took an incredible step in
evolution, when animals learned to build skeletons. Using many different
materials, from calcium carbonate and phosphate, and even silica, to
make shell and bone, they started creating the support structures that
are now critical to most living forms, providing rigidity and strength.
Manifesting in a vast variety of forms, they provided the framework for
sophisticated networks of life that fashioned the evolution of Earth's
oceans, land, and atmosphere. Within a few tens of millions of years,
all of the major types of skeleton had appeared.
Skeletons enabled an unprecedented array of bodies to evolve, from the
tiniest seed shrimp to the gigantic dinosaurs and blue whales. The
earliest bacterial colonies constructed large rigid structures -
stromatolites - built up by trapping layers of sediment, while the
mega-skeleton that is the Great Barrier Reef is big enough to be visible
from space. The skeletons of millions of coccolithophores that lived in
the shallow seas of the Mesozoic built the white cliffs of Dover. These,
and insects, put their scaffolding on the outside, as an exoskeleton,
while vertebrates have endoskeletons. Plants use tubes of dead tissue
for rigidity and transport of liquids - which in the case of tall trees
need to be strong enough to extend 100 m or more from the ground. Others
simply stitch together a coating from mineral grains on the seabed.
In Skeletons, Jan Zalasiewicz and Mark Williams explore the incredible
variety of the skeleton innovations that have enabled life to expand
into a wide range of niches and lifestyles on the planet. Discussing the
impact of climate change, which puts the formation of some kinds of
skeleton at risk, they also consider future skeletons, including the
possibility that we might increasingly incorporate metal and plastic
elements into our own, as well as the possible materials for skeleton
building on other planets.
