1 Introduction
Human beings have consciousness, and some other organisms may have consciousness too.
Organisms and their traits are products of biological evolution. This chapter is about how con-
sciousness might have evolved, and why.
We begin in Section 2 by clarifying that our main topic is phenomenal consciousness—the
ways our subjective experiences feel—rather than any functional or neural correlates thereof.
In Section 3 we point out that there are several ways that a biological trait such as phenomenal
consciousness might have arisen during evolution: it might have been selected for because it
performs an adaptive function, it might have arisen as a byproduct of some other trait, or it
might be the result of random genetic drift. If phenomenal consciousness performs a function,
such a function must be identified; Section 4 considers what consciousness might be an adapta-
tion for but adds that identifying the function of phenomenal consciousness is harder than it
seems. Section 5 considers how phenomenal consciousness might have originated during evolu-
tion if it has no function. Section 6 wraps things up.2 On “Consciousness”
Consciousness is a notoriously difficult topic. One reason is that the term is ambiguous: different
philosophers and scientists use the term “consciousness” to pick out different mental phenom-
ena. Another reason is that even when we disambiguate “consciousness,” the referent of the term
is often nebulous. The reason is twofold. First, whatever one means by “consciousness,” it is a
mental phenomenon, and mental phenomena are difficult to observe and conceptualize. Second,
some phenomena that are referred to as “consciousness” are private in the sense that each sub-
ject experiences only her own consciousness and not the consciousness of anyone else. Because
of this privacy, some theorists deny that consciousness is real, or at least that it’s an appropriate
subject of scientific investigation.
Here, by “consciousness” we mean phenomenal consciousness or qualia, as philosophers have
sometimes labeled the phenomenon: the qualitative feel of being in, or having, particular men-
tal states; the quality of “what-it’s-like” to be in or have those states. Philosophers distinguish
between creature consciousness and state consciousness. Creature consciousness is the property of28
THE BIOLOGICAL EVOLUTION
OF CONSCIOUSNESS
Corey J. Maley and Gualtiero Piccinini
Corey J. Maley and Gualtiero Piccinini The Biological Evolution of Consciousness