From finches to families: how evolution shaped life and made each of us unique.

Life on Earth is built from the same particles and governed by the same laws as the wider Universe – but biology reveals how those laws produce living, changing organisms. Darwin’s theory of evolution by natural selection explains how species adapt, flourish, and fade. Genetics later revealed the code that carries those adaptations forward, shaping every living being. Today, we know that each of us is a product of both our inherited genes and our lived experience. Life, in all its complexity, is fully explainable within the natural order – and that makes it no less remarkable.

Evolution: Darwin’s Big Idea

Replicate. Vary. Select. The three steps that drive all of life.

In a competitive world, organisms with advantageous characteristics survive and reproduce more.

Over generations, these characteristics spread while weaker ones fade.

The process can be summed up in 3 steps: Replicate; Vary; Select.

Example: The Grants’ 20-year finch study in the Galapagos showed beak sizes shifting as droughts or rains changed the available food supply.

The Tree of Life

Darwin’s Tree of Life shows we are all branches of the same story.

• All living things trace back to a single common ancestor.
• Darwin sketched this Tree of Life to show how species branch and diverge.

Genetics later confirmed it, allowing us to map:

• All humans alive today share a common ancestor \~150,000 years ago.
• Humans split from chimpanzees/bonobos \~7 million years ago.
• Apes split from monkeys \~21 million years ago.

Genetics: The Mechanism of Inheritance

We are survival machines, carrying forward the successful genes of the past.

• Genes contain the instructions for proteins, the building blocks of life.
• Genes influence appearance, health, intelligence, temperament, personality.
• Environment and experiences modify how genes are expressed – switching them on or off.
• Richard Dawkins called organisms survival machines carrying successful genes forward.

Nature & Nurture: Making Us Us

Genes don’t determine everything – they provide propensities, shaped by experience.

• Each person inherits a unique set of genes.
• Some traits (like eye colour) are almost entirely genetic.
• Most traits are shaped by both genes and environment.
• We are products of nurture acting on nature.

The Big Picture

Life, like the Universe itself, can be fully explained without recourse to the supernatural. Evolution and genetics together account for the diversity of species and the uniqueness of individuals.