Hallmarks of Design

Evolution is based on a key assumption that all the mechanisms within organisms can evolve incrementally so all intermediate mechanisms have some useful function.

A mechanism that can evolve one characteristic at a time while always having a useful function can be termed an reducible mechanism.

A mechanism that cannot evolve one characteristic at a time while always having a useful function can be called an irreducible mechanism. Irreducible mechanisms point to a Designer, and represent one of the most powerful arguments against evolution, because evolutionists fully admit that the process of evolution cannot produce an irreducible mechanism.

Darwin himself admitted that evolution could not produce an irreducible mechanism. In his Origin of Species, Darwin said: 'If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.'

The human knee joint

There are three main types of limb joint in animals and humans. These are the ball and socket joint (hip and shoulder), the pivot joint (elbow) and the condylar (knee). The knee joint is the largest and most complex joint in the human body. The knee is called a condylar joint because of the rolling and sliding action (articulation) between the upper leg bone (the femur) and the main lower leg bone (the tibia), as shown in figures 1.2 and 1.3. The femur bone has two protrusions, called condyles, which have a convex curvature so they can roll and slide against the tibia bone. The tibia has two concave grooves that match the condyles of the femur bone. The two central ligaments that connect the tibia to the femur are called cruciate ligaments because of the way they form a cross. The cruciate ligaments fit neatly inside the space between the two condyles.

The knee joint is an irreducible mechanism that cannot evolve because it requires four complex parts to exist simultaneously and in a complex assembly to be able to perform its basic function. The four parts are interdependent with each other in complex ways and must always exist together to be of any use. The two bones are essential be-cause they perform the sliding and rolling motion. The two cruciate ligaments are essential, because they act as mechanical linkages and perform a vital guiding function in the joint, as shown in figure 1.3. If just one ligament is removed, then the joint cannot function as a hinge, and the joint has no other useful function.

Critical characteristics

The irreducibility of the knee joint is most clearly demonstrated by identifying a set of characteristics that must exist simultaneously for the knee to have any useful function. These are termed critical characteristics.

Critical characteristics must not only be simultaneously present, but they must also be precisely compatible with each other in order to produce the required physical effects. In general, the critical characteristics of mechanical mechanism are often geometrical characteristics because these must have precise values, whereas other characteristics such as material properties usually do not have to have precise values. The advantages of identifying an irreducible set of critical characteristics is that they give an indication of the minimum quantity of information in the genetic code that must exist simultaneously and correctly.

Genetic code

The knee has many critical geometrical characteristics because the two cruciate ligaments and the two leg bones form a very sophisticated and precise mechanism, called a four-bar hinge. This four-bar hinge is shown at various stages of rotation in figure 1.3, and figure 1.4 shows clearly how the four-bar hinge works. The knee joint is a particularly sophisticated kind of four-bar hinge because the cruciate ligaments are not rigid and have to be kept taut by the rolling action of the bones.

There are at least 16 critical characteristics in the knee joint as shown in table 1.1. These will be specified by about 16 genes in the genetic code. The critical characteristics are geometrical characteristics absolutely essential to the joint.

If one of the characteristics shown in table 1.1 is missing, then the knee cannot function at all. Anyone who has experienced a ruptured cruciate ligament or broken leg bone will know this only too well. The 16 characteristics must not only be present, but be precisely compatible with each other to produce the right physical motion. The two bones must have a compatible curvature at their interface, which must be precisely compatible with the position and movement of the cruciate ligaments.

If the attachment points are not in the right place on the bones, then the instantaneous centre of rotation of the knee joint will not be compatible with the shape of the bones, and the knee will seize up or fall apart. The ligaments must also be assembled to the correct attachment points so that the ligaments form a cross as shown in figures 1.3 and 1.4. If one of the ligaments was assembled to the wrong attachment point such that the cross was not formed, then the knee could not function as a hinge and would be useless.

As a human characteristic is specified typically by one gene with the order of 1,000 chemical units of information, it requires many thousands of units of information in the genetic code to specify the essential design information of the four-bar hinge. The theory of evolution proposes that gene mutation causes random changes to single units of information in the genetic code and that this leads to evolution. Yet, in the case of the knee, many thousands of precise units of information must be in place simultaneously for the knee to have any usefulness.

Not only must all critical characteristics be present from the start, but they must also remain unchanged, because otherwise this will cause the physical system to break down. In the case of a healthy knee joint, if a random change is made to one of the critical characteristics, such as the position of a ligament, then the knee will cease to function properly, because the position of the ligament is no longer compatible with other critical characteristics. This shows why random gene mutations generally cause malfunctions and suffering in living organisms.

Impossibility

The knee joint presents a major challenge to the evolutionist because it is irreducible, and because there are no intermediate forms of joint between a condylar joint and the two other joints found in animals and humans: the ball and socket joint and the pivot joint.

It is very difficult for the evolutionist to explain how an evolutionary process could cause two ligaments to suddenly become crossed at the centre of a pivot precisely at the same time that a space is formed to accommodate them, and precisely at the same time that a complex and compatible rolling motion is formed! The popular evolutionist, Dawkins, claims that he is not aware of any type of complex organ that could not have evolved by 'numerous successive slight modifications'. However, the knee joint is just one clear example of a mechanism within the human body that could not have evolved by numerous successive slight modifications.

It is important to be aware that the process of evolution cannot produce an irreducible system whether the incremental change are random or planned. This means that evolution cannot work even if an intelligent being is able to choose which genes should mutate. Therefore, evolution is impossible whether it is atheistic evolution (mutations are random) or theistic evolution (God uses mutations to create).

Some evolutionists have recently claimed that evolution occurs in a punctuated equilibrium, i.e. there are periods of stability followed by relatively rapid change. It is important to realise, however, that punctuated equilibrium does not in any way change the fact that evolution relies on an accumulation of single gene mutations. Punctuated equilibrium simply postulates that there are long periods when there are few selective pressures, and then short periods of intense selective pressures.

Non-essential parts

Even though the fine details of the knee joint give evidence of design, it is only the irreducible mechanism of the knee that can 'prove' the theory of evolution to be impossible. Evolutionists such as Richard Dawkins, are experts at focussing attention on non-critical parts. For example, Dawkins places much attention on how the lens in the human eye is not essential to the basic functioning of the eye, and how this supposedly supports the idea that the eye could have evolved. If evolutionists attempted to discuss the evolution of the knee, there is no doubt they would describe in detail how the knee-cap was not absolutely essential, and how it just appeared and was retained because it gave advantages. After giving many such examples, they might deceive the reader into thinking that every single part of the knee could just evolve by chance. It is therefore very important to emphasise that there is an irreducible mechanism at the core of the knee joint.

When discussing evolution, biology books will rarely distinguish between critical and non-critical characteristics in an organism, despite the fact that characteristics are known to vary greatly in importance. This is surprising because a characteristic like the attachment position of a ligament is vastly more important than the colour of the ligament. There is no doubt that the obscuring of critical characteristics is done because evolutionists can only attempt to give trivial examples of evolution such as changes of colour.

To prove the theory of evolution, the evolutionist would have to show how a critical characteristic like the attachment position of the cruciate ligaments could evolve. However, this has never been done and can never be done because such a critical characteristic could not evolve in isolation.

This article is taken from Hallmarks of Design by Stuart Burgess, recently published by Day One at £6.99, and is used with permission.

Dr. Stuart Burgess lectures in Engineering Design at Bristol University.

© Evangelicals Now - May 2000
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