Rationale and purpose

The purpose of the publication is
encapsulated in the expression:
"physics of living populations".
What meaning do we wish to give to this expression?
To begin with, let us offer three short answers.

 * We are all familiar with the term ``biophysics''.
In this field some concepts of physics are used
to understand biological systems. For instance, the
rules of mechanics may explain how the knee joint
works.  Here, the term ``physics'' will have a
similar meaning except that our main source of inspiration
will be the broad experimental methodology of physics
rather than any specific field of physics.

 * The second answer is rather a disclaimer.
In order to prevent possible
misunderstandings it should be emphasized that
mentioning physics does
NOT mean that one wishes to transpose and apply the
existing mathematical
framework of physics to living populations.

 * The third short answer is that
``physics'' is understood here in the same way as in the
title of a book published in 2011 by Cambridge University
Press, namely: ``The Physics of Foraging''. The present
archive shares many of the objectives outlined by the authors
in their introduction.

The usefulness of and need for such a publication can be
quickly perceived by browsing through present-day issues of
biological journals. For instance in entomological
journals one will find a host of specialized studies, each
of which focuses
on one aspect of a specific activity of a specific species.
A physical analogue would be to study in detail
one aspect of the fall
of a specific variety of apples without trying to identify
the law which governs the fall of all apples.
Studies focusing on just
one apple variety can of course be of interest for the purpose of  orchard farming but they
will never lead to the law of gravitation brought to light by
Galileo and Newton. This law, which 
is the root-mechanism which governs
the fall in air of all fruits and indeed of all objects,
can be found by comparing the
falls of various fruits and by searching what
property they have in common.

The identification of a core-mechanism is by no means
restricted to such ``hard sciences'' like physics or chemistry. 
As a matter of fact,
medicine is based on the very same approach. While two
patients with Alzheimer disease will not display
exactly the same symptoms, the definition of the disease
will rely on shared features. Taken together,
such core-features will constitute what is called the
Alzheimer syndrome.
For the case of falling bodies it turns out
that the law can be stated in mathematical form.
However, mathematics is not an essential requirement.
As shown by
the Alzheimer example, the core-mechanism may also be
stated in a semi-quantitative way.

For some diseases,
e.g. the Down syndrome (trisomy 21), the core-mechanism is well
understood, while for others it is not.
Very likely one will meet a similar situation in the
investigation of the core-mechanisms of the behavior of
living populations. While in some cases a clear understanding
of the core-mechanism will emerge, in others one will
have to content oneself with a qualitative or semi-quantitative
description. This should not come as a surprise. After all,
even though the law governing falling bodies
has been discovered four centuries ago we still
do not understand clearly the real mechanism of gravitation.
On account of the bewildering diversity of living organisms
it will certainly be a challenge to find
clear-cut regularities. 

A well-known saying tells us that 
``there is a crack in everything and that's how the
light gets in''. 
Let's hope that the present undertaking will be
able to shed some light in this promising field.