Environmental Engineering Reference
In-Depth Information
4
Population
Control
Evolution and Biodiversity
Biodiversity
CASE STUDY
How Did We Become
Such a Powerful Species
So Quickly?
in the dark. Our ears cannot pick up low-pitched
sounds like the songs of whales as they glide through
the world's oceans. We cannot smell as keenly as a dog
or a wolf. By such measures, our physical and sensory
powers are pitiful.
Yet humans have survived and flourished within
less than a twitch of the 3.7 billion years that life has
existed on the earth. Analysts attribute our success to
three adaptations: strong opposable thumbs that allow
us to grip and use tools better than the few other ani-
mals that have thumbs, an ability to walk upright, and
a complex brain (Figure 4-1). These adaptations have
helped us develop technologies that extend our lim-
ited senses, weapons, and protective devices.
In only a short time, we have developed many
powerful technologies to take over much of the earth's
life-support systems and net primary productivity to
meet our basic needs and rapidly growing wants. We
named ourselves Homo sapiens sapiens —the doubly
wise species. If we keep degrading the life-support
system for us and other species, some say we should
be called Homo ignoramus. During this century we
will probably learn which of these names is more
appropriate.
The good news is that we can change our ways.
We can learn to work in concert with nature by under-
standing and copying the ways nature has sustained
itself for several billion years despite major changes in
environmental conditions. This means heeding Aldo
Leopold's call for us to become earth citizens, not
earth rulers.
To do so, we need to understand the basics of
biological evolution, including how it affects the
earth's biodiversity as species come and go and new
ones arise to take their place. Here is the essence of
this chapter. Each species here today represents a long
chain of genetic changes in populations in response to
changing environmental conditions. And each species
plays a unique ecological role (called its niche ) in the
earth's communities and ecosystems
Like many other species, humans have survived and
thrived because we have certain traits that allow us to
adapt to and modify the environment to increase our
survival chances. What are these adaptive traits?
First, consider the traits we do not have. We lack
exceptional strength, speed, and agility. We do not
have weapons such as claws or fangs, and we lack a
protective shell or body armor.
Our senses are unremarkable. We see only visible
light—a tiny fraction of the spectrum of electromag-
netic radiation that bathes the earth. We cannot see
infrared radiation, as a rattlesnake can, or the ultra-
violet light that guides some insects to their favorite
flowers.
We cannot see as far as an eagle or in the night like
some owls and other nocturnal creatures. We cannot
hear the high-pitched sounds that help bats maneuver
Figure 4-1 Humans have thrived as a species mostly because
of our complex strong opposable thumbs (left), our ability to
walk upright (right), and our complex brains.
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