One
very common claim is that DNA is a blueprint that lays out the
complete specification of the human body. Another common claim is
that DNA is a recipe (or a library of recipes) for making an
organism. It is also sometimes claimed that DNA is like a computer
program for generating our bodies.
But
such statements are not warranted by the facts. Judging from the
facts, we must conclude that while DNA uses a code of symbolic
representations (the genetic code), DNA is not a blueprint for making
a human, is not a recipe for making a human, and is not a program or
algorithm for making a human. The facts indicate that DNA is not
anything close to a complete specification of an organism, but that
DNA is instead something much simpler, mainly just a kind of database
(or a collection of ingredient lists) used in making particular parts
of an organism.
To
get an idea of the true nature of DNA, it is a good idea to adopt a
conceptual model of DNA. In science, a model is a somewhat simplified
representation that helps us understand a more complicated reality. A
classic example of a model is the Bohr model of the atom, in which
the nucleus of an atom is compared to the sun, and the electrons in
an atom are compared to planets that revolve around the sun. The
atom is actually more complicated than such a situation (given the
weirdness of quantum mechanics), but the Bohr model is still useful
to help us get a basic grasp of what an atom is like. The Bohr model
is essentially accurate, because just as the great majority of a
solar system's mass exists at its center in the sun, the great
majority of an atom's mass exists at its center in the atomic
nucleus.
Now,
what model can we use to grasp the basic nature of DNA? A good model
to use is what we may call the chain-of-colored-beads model. Let us
imagine a long chain of colored beads, in which there are about
twenty possible bead colors, and each bead stands for a particular
type of chemical called an amino acid. That is exactly how DNA
works. We can imagine that one of these colors means kind of
“Start.” The amino acids are the constituents of proteins. So
after one of these “Start” beads appears in the chain, there is then a sequence of colored beads, with each color representing one of
the twenty amino acids. Altogether the long “chain of beads”
that is DNA specifies the ingredients of thousands of different
proteins.
A
particular snippet or section of DNA will correspond to a chain of
amino acids that is the starting point of a protein. The visual
below illustrates this schematically.
An
example of one-dimensional information is a telephone number, a
social security number, or a stock ticker tape. Such information can
always be presented with a single line or row, although some types of
one-dimensional information might require a long line or row. A more
complicated type of information is what is called two-dimensional
information. Such information requires both rows and columns. An
example of two-dimensional information is the information in a
calendar or a spreadsheet.
Another
more complicated type of information is called three-dimensional
information. Three-dimensional information specifies something that
can only be described using the dimensions of length, width, and
depth. An example is the information specifying the three-dimensional
structure of a car.
Now,
what type of information would be required to specify the physical
layout of a three-dimensional body such as the human body? To specify
such a thing, you would need three-dimensional information,
information involving length, width and depth. But there is no way that such three-dimensional information could exist in DNA, which has merely one-dimensional
information.
In
fact, it seems that in order to make a complete biological
specification of an organism, you would need not just
three-dimensional information, but four-dimensional
information. Time is often regarded as the fourth dimension. We can
describe four-dimensional information as information that involves
not merely aspects of length, width, and depth, but also an aspect of
time.
Why
would you need four-dimensional information to specify an organism
such as a human? For one thing, it is not true that humans just pop
into existence as adults. Instead, there is a long series of
transitions between the earliest state of a newly fertilized egg, and
that of a full-grown human. A full human specification would have to
specify each of these states. So the specification would need to use
the fourth dimension of time to specify this temporal progression in
human forms.
Another
reason why a full human specification would need to be
four-dimensional is that human beings are not static objects, but
intensely dynamic objects. Think of all the dynamic activity
occurring every day in your body. Blood and electricity is flowing
about, proteins are being synthesized according to specific time
tables, cells are being born and dying according to other time
tables, and so forth. A single snapshot of the state of a human body
is not at all sufficient to capture this dynamic activity. You would
need to have a specification that is four-dimensional. Similarly, if
someone from some small island in the Pacific had no idea of what a
city was, you would never specify what a city was by just showing
some maps. You would need to somehow specify the motion occurring in
the city: the subways moving, the cars moving, the people moving, the
water flowing through pipes, and so forth.
But
DNA can only specify one-dimensional information. So it is very
absurd to maintain that a biological specification of humans is in
the one-dimensional information of DNA.
The
table below lists on the left various types of information that would
be needed to have a full biological specification of an organism, and
on the right whether or not such information can be specified in DNA.
| Type of information | Can it be specified in DNA? |
| Linear amino acid sequence of a protein molecule | Yes |
| Three-dimensional shape of a protein molecule | No |
| Exact location where a protein is located in body | No |
| Layout of a cell organelle | No |
| Layout of a cell | No |
| Layout of a tissue type | No |
| Layout of an organ | No |
| Layout of an organ system | No |
| Layout of a full body plan | No |
| Structure progression from simplest tiniest form to fully grown form | No |
| Dynamic behavior inside an organism during a particular month or year | No |
Some
would disagree about the answer I have given in the third row, and
claim that the three-dimensional shape of a protein molecule is
purely a consequence of its sequence of amino acids. If this were
true, scientists would have long ago solved the protein folding
problem, and would be able to predict the three-dimensional shapes of
proteins from their one-dimensional sequence of amino acids. But
after decades of trying to do this, the protein-folding problem is
still unsolved, and (as discussed here) scientists still cannot accurately predict the 3D
shapes of large proteins from their amino acid sequences.
The
fact that DNA can only store one-dimensional information is a
decisive reason for rejecting all claims that DNA even half-specifies
the human organism. There are two other reasons for rejecting such
claims. The first is that no one has found any information in DNA
corresponding to human body plan information. The human genome has
been thoroughly studied through massive projects such as the Human
Genome Project and the ENCODE project. No one has found any gene
information specifying a human body plan, a structural plan for a
cell, a structural plan for an organ, or a structural plan for an
organ system.
The
second reason is equally enormous. It is simply that there exists
nothing in the human body that could interpret a specification of
human biology, if such a thing existed in DNA. Consider computer
code. Such code can only work because there is an enormously
sophisticated piece of software called an interpreter or compiler
that is smart enough to read such complex instructions. If it were to
happen that DNA stored instructions for making a human, contrary to
the evidence, we would only explain human development if we imagined
that somewhere in our biology was some enormously sophisticated
machinery or functionality capable of reading such highly complex
instructions and executing them. But no such functionality has ever
been discovered.
Is
it accurate to say that there are recipes in DNA? No it is not. A
recipe includes an ingredient list, and a set of instructions
explaining how to make a particular meal or dish using those
ingredients. DNA has lots of ingredient lists specifying the
ingredients of proteins. But nowhere does DNA specify a series of
instructions for assembling a protein molecule, a cell, an organ, an
organ system, or a full body. Protein molecules have
three-dimensional shapes that they assume for unknown reasons. Such
shapes are not specified in DNA.
At the end of this post (in which I cite additional very weighty reasons for rejecting the claim the DNA is a specification of a human), I quote eight different scientists (mainly biologists) who state that DNA is not a recipe or blueprint for making a human, or anything like a specification of the human form.
So
where is it that biological shapes and structures come from? This is
a gigantic unknown, which stands as a dramatic contradiction of all
attempts to explain biology in mechanistic or materialistic terms. We
do not know where the 3D shapes of protein molecules come from. We do
not know where the shapes of cells come from. We do not know where
the structure of tissues comes from. We do not know where the shapes of
organs come from. We do not know where the shapes of organ systems
come from. We do not know where the overall body plan of an organism
comes from. We therefore have a strong reason to suspect that such things are
mysterious inputs from some unfathomable reality outside of an
organism.
The
reality of DNA is something very inconsistent with the claims about
DNA made by many a science book, where we hear about DNA as a
blueprint for the body or DNA as some recipe for making a human. In
my next post I will look at one of these books, and the false and
wildly inconsistent claims the book makes about DNA. We
will see that the tall tales that the book tells about DNA are five
different claims that are all inconsistent with each other, resulting
in a kind of DNA mythology that is “all over the map.”
Postscript: The genome is an organism's DNA, while the phenotype is the set of observable characteristics of an organism (such as its external appearance and internal arrangement of organs). In the mainstream book "Frontiers in Ecology, Evolution and Complexity," a scientist states the following:
At the beginning of the 21st century, biology confronted an uncomfortable fact: despite the increasing availability of whole genome sequence data, it was not possible to predict, or even clarify, phenotypic observations. In fact, we now know that there is not sufficient information in the linear DNA of the complete genomes to recover and/or understand the diverse phenotypic states of an organism.
In statements such as this, scientists "fess up" that the idea of DNA as a human specification is not true. Another example can be found in this paper written by several scientists, in which we read this: "Because genes code for proteins, there are no 'genes for' phenotypes per se, including behavioral phenotypes."
Postscript: The genome is an organism's DNA, while the phenotype is the set of observable characteristics of an organism (such as its external appearance and internal arrangement of organs). In the mainstream book "Frontiers in Ecology, Evolution and Complexity," a scientist states the following:
At the beginning of the 21st century, biology confronted an uncomfortable fact: despite the increasing availability of whole genome sequence data, it was not possible to predict, or even clarify, phenotypic observations. In fact, we now know that there is not sufficient information in the linear DNA of the complete genomes to recover and/or understand the diverse phenotypic states of an organism.
In statements such as this, scientists "fess up" that the idea of DNA as a human specification is not true. Another example can be found in this paper written by several scientists, in which we read this: "Because genes code for proteins, there are no 'genes for' phenotypes per se, including behavioral phenotypes."