Longman GCSE Biology

Longman GCSE Biology. Bradfield, P., and S. Potter. 2002.

Evidence for evolution

This textbook claims, that Homology gives evidence for common ancestry. It shows the pentadactyl limb structure of humans, birds and bats, and states:

These bones are known as homologous structures. They show that all three groups of animals have evolved from a common ancestor with the basic pentadactyl limb structure.

The Peppered Moth is used as an example of natural selection, though the limitations to the data are acknowledged in a text box:

Recently some biologists have questioned the methods by which the peppered moth data was obtained. They do not, however, think that the conclusion about the way in which natural selection is thought to operate is necessarily wrong. They think that it presents a picture that is too clear cut and further data, obtained in a more rigorous manner, is needed to support the conclusion.

Bacterial Resistance to antibiotics is also used as an example of natural selection, as is Sickle Cell Anaemia.

This textbook also uses evidence from comparative Embryology, with a diagram given showing ‘gill pouches’ in bird, reptile, human and pig embryos.

Comparing the ways in which the embryos of different animals develop can give clues about how closely related they are. It also reveals remarkable common features. Human embryos have structures resembling gills for a brief period in their development.

Embryos never have gills, and calling features of human embryos 'gill slits' is merely to read Darwinian theory into the evidence.

That 98% of our DNA is the same as that of the chimpanzee is claimed to provide evidence for evolution. For a critique of this see: Comparative Genetics and Biochemistry.

Similarities between placental and marsupial mammals are used as evidence that natural selection has operated in the same way on different animals in similar environments.

Fossils are used as evidence for evolution: Sometimes fossils in successive layers show gradual changes . An example given of this is horse evolution, with a diagram showing changes in size, teeth and feet. Nothing is said about limitations of fossil record in this book.

Teaching the controversy?

This text does not claim that there is consensus among scientists over evolution, but it does not present any alternative views.

Humans have been asking the question 'Where did we come from?' for thousands of years. The theory of evolution, occuring by natural selection, is the most widely accepted scientific explanation of the answer to this question.

Many biologists now believe that there is sufficient evidence to suggest that evolution has followed the general course outlined below:
Life began in water as a result of reactions between chemicals in the early Earth's atmosphere and oceans.
The first life forms were unicells (single cells), similar to bacterial cells.
These unicells became more complex as the cells acquired more and more organelles (such as mitochondria and chloroplasts).
Simple multicellular organisms became more and more complex, giving rise to plants, animals, fungi and other types of organisms.
Some of these organisms colonised the land and the evolution of land animals, plants and fungi began.

Very little evidence is given for any of these claims. Pupils are expected to believe them on the basis that most biologists now believe.... Is science about listening to authority figures, or weighing up evidence? What do the biologists who do not believe in evolution believe? The reader is not told.

Quote

Evolution by natural selection...has lately come to function more as an antitheory, called upon to cover up embarrassing experimental shortcomings and legitimize findings that are at best questionable and at worst not even wrong.

Robert B. Laughlin, A Different Universe (New York: Basic Books, 2005)

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