In both sides of the debate regarding Teleology or the role of purpose in science (and even courts in their decisions) Karl Popper's criterion of falsifiability (see Daubert standard have frequently been invoked. Here we begin to write and research about these ideas.
In this context, passages written by Popper are frequently quoted in which he speaks about such issues himself. For example, he famously stated
Darwinism is not a testable scientific theory, but a metaphysical (Metaphysics) research program—a possible framework for testable scientific theories.
He continued:
And yet, the theory is invaluable. I do not see how, without it, our knowledge could have grown as it has done since Darwin.In trying to explain experiments with bacteria which become adapted to, say, penicillin, it is quite clear that we are greatly helped by the theory of natural selection.
Although it is metaphysical, it sheds much light upon very concrete and very practical researches. It allows us to study adaptation to a new environment (such as a penicillin-infested environment) in a rational way: it suggests the existence of a mechanism of adaptation, and it allows us even to study in detail the mechanism at work.
He also noted that theism, presented as explaining adaptation:
was worse than an open admission of failure, for it created the impression that an ultimate explanation had been reached.
Popper later said:
When speaking here of Darwinism, I shall speak always of today's theory—that is Darwin's own theory of natural selection supported by the Mendelian theory of heredity, by the theory of the mutation and recombination of genes in a gene pool, and by the decoded genetic code.This is an immensely impressive and powerful theory. The claim that it completely explains evolution is of course a bold claim, and very far from being established. All scientific theories are conjectures, even those that have successfully passed many severe and varied tests.
The Mendelian underpinning of modern Darwinism has been well tested, and so has the theory of evolution which says that all terrestrial life has evolved from a few primitive unicellular organisms, possibly even from one single organism.
In 1974, regarding DNA and the origin of life he said:
What makes the origin of life and of the genetic code a disturbing riddle is this: the genetic code is without any biological function unless it is translated; that is, unless it leads to the synthesis of the proteins whose structure is laid down by the code. But, as Monod points out, the machinery by which the cell (at least the non-primitive cell, which is the only one we know) translates the code "consists of at least fifty macromolecular components which are themselves coded in the DNA.(Monod, 1970;[53] 1971, 143[54]).
Thus the code can not be translated except by using certain products of its translation. This constitutes a really baffling circle; a vicious circle, it seems, for any attempt to form a model, or theory, of the genesis of the genetic code.Thus we may be faced with the possibility that the origin of life (like the origin of the universe) becomes an impenetrable barrier to science, and a residue to all attempts to reduce biology to chemistry and physics.
He explained that the difficulty of testing had led some people to describe natural selection as a tautology (tautology (logic)), and that he too had in the past described the theory as "almost tautological", and had tried to explain how the theory could be untestable (as is a tautology) and yet of great scientific interest:
My solution was that the doctrine of natural selection is a most successful metaphysical research programme. It raises detailed problems in many fields, and it tells us what we would expect of an acceptable solution of these problems. I still believe that natural selection works in this way as a research programme. Nevertheless, I have changed my mind about the testability and logical status of the theory of natural selection; and I am glad to have an opportunity to make a recantation.
Popper summarized his new view as follows:
The theory of natural selection may be so formulated that it is far from tautological. In this case it is not only testable, but it turns out to be not strictly universally true.There seem to be exceptions, as with so many biological theories; and considering the random character of the variations on which natural selection operates, the occurrence of exceptions is not surprising.
Thus not all phenomena of evolution are explained by natural selection alone.
Yet in every particular case it is a challenging research program to show how far natural selection can possibly be held responsible for the evolution of a particular organ or behavioural program.
These frequently quoted passages are only a very small part of what Popper wrote on the issue of evolution, however, and give the wrong impression that he mainly discussed questions of its falsifiability. Popper never invented this criterion to give justifiable use of words like science. In fact, Popper says at the beginning of ''Logic of Scientific Discovery'' that it is not his aim to define science, and that science can in fact be defined quite arbitrarily.
Popper had his own sophisticated views on evolution that go much beyond what the frequently-quoted passages say. In effect, Popper agreed with some of the points of both creationists and naturalists, but also disagreed with both views on crucial aspects. Popper understood the universe as a creative entity that invents new things, including life, but without the necessity of something like a god, especially not one who is pulling strings from behind the curtain. He said that evolution must, as the creationists say, work in a goal-directed way but disagreed with their view that it must necessarily be the hand of god that imposes these goals onto the stage of life.
Instead, he formulated the spearhead model of evolution, a version of genetic pluralism. According to this model, living organisms themselves have goals, and act according to these goals, each guided by a central control. In its most sophisticated form, this is the brain of humans, but controls also exist in much less sophisticated ways for species of lower complexity, such as the amoeba. This control organ plays a special role in evolution—it is the "spearhead of evolution". The goals bring the purpose into the world. Mutations in the genes that determine the structure of the control may then cause drastic changes in behaviour, preferences and goals, without having an impact on the organism's phenotype. Popper postulates that such purely behavioural changes are less likely to be lethal for the organism compared to drastic changes of the phenotype.
Popper contrasts his views with the notion of the "hopeful monster" that has large phenotype mutations and calls it the "hopeful behavioural monster". After behaviour has changed radically, small but quick changes of the phenotype follow to make the organism fitter to its changed goals. This way it looks as if the phenotype were changing guided by some invisible hand, while it is merely natural selection working in combination with the new behaviour. For example, according to this hypothesis, the eating habits of the giraffe must have changed before its elongated neck evolved. Popper contrasted this view as "evolution from within" or "active Darwinism" (the organism actively trying to discover new ways of life and being on a quest for conquering new ecological niches),Philosophical confusion? – Science Frontiers 
with the naturalistic "evolution from without" (which has the picture of a hostile environment only trying to kill the mostly passive organism, or perhaps segregate some of its groups).
Popper was a key figure encouraging patent lawyer Günter Wächtershäuser to publish his Iron–sulfur world theory on abiogenesis and his criticism of "soup" theory (Primordial soup).
About the creation-evolution controversy, Popper wrote that he considered it "a somewhat sensational clash between a brilliant scientific hypothesis concerning the history of the various species of animals and plants on earth, and an older metaphysical theory which, incidentally, happened to be part of an established religious belief" with a footnote to the effect that "[he] agree[s] with Professor C.E. Raven when, in his ''Science, Religion, and the Future'', 1943, he calls this conflict "a storm in a Victorian tea-cup"; though the force of this remark is perhaps a little impaired by the attention he pays to the vapours still emerging from the cup—to the Great Systems of Evolutionist Philosophy, produced by Bergson, Whitehead, Smuts, and others."