1. Fossil Record (pre-1859) What did the fossil record show?
2. Darwin's Theory (1859 - 1900's) How did Darwin explain variety?
3. Gene Theory (1900's -1930's) What did gene theory explain?
4. New Synthesis (1930's - 1970's) What is the New Synthesis?
5. New Debate (1970's - present) Why is the debate still going?

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HISTORY

THE THEORY

RESULTS

1 Fossil Record (pre-

1859)

Millions of species have existed, but they appeared suddenly, and persisted unchanged for huge periods.

Fossil record showed that over time, new types arose and others went extinct, but it seemed to occur in 'steps'.

This sudden appearance of new types allowed people to retain belief in Biblical Creation, only this could not explain the huge variety of species.

2 Darwin's Theory (1859 - 1900's)

New types could evolve slowly by incremental adaptation. This is how so many varieties came to populate the Earth.

Sudden appearance was only an effect of many small changes over huge periods.

Darwin did not explain how inherited variety arose and persisted. But he believed a complete fossil record would show many intermediate types.

3 Gene Theory (1900's -1930's)

Showed hereditary variety came in discreet packets. So new varieties can arise and will persist.

Genes allow variety to arise by mutation, and be passed on as distinct traits.

Although genes explained variety and persistence, problem remained that most traits (like size) were continuously variable and adaptable.

4 New Synthesis (1930's - 1970's)

New models showed small discrete changes in genes would spread through populations.

Small changes will accumulate as a continuous effect.

Darwin's thesis of continuous small accumulation is shown to be consistent with latest models of gene flow.

5 New Debate (1970's - present)

Fossil record still shows evolution mostly in bursts, with long periods of stability.

Periods of "evolution" up to 1,000 times faster than periods of "stasis".

Models of gene flow (New Synthesis) now well proven, but debate if these alone can explain the stepped changes.