One of the earliest memories from my childhood is getting kicked out of Sunday School.

I remember the basement classroom of the suburban church, with its beige cinder block walls and Bible-themed coloring books, and the discomfort I felt at the age of five.

The teacher was deep into a lesson about Adam and Eve when I asked, "What about evolution?"

I had heard of Charles Darwin and his theories and they didn’t jibe with the teacher's story about the creation of humans from clay and a rib.

Evolution, rather than the unifying concept of biology, was heresy in that classroom.

I never returned to Sunday school, but I did develop a lifelong interest in the 7 million-year-old mystery of how Homo sapiens came to be Earth’s dominant species.

The theory of evolution simply describes how living things change over time, adapting to conditions through the process of natural selection - not too controversial really.

Embracing evolution also allows us to ask fun questions about our earliest ancestors: What did they look like? Why did they descend from trees and take to walking upright? What led humans to develop language, analytical skills, family structures, foibles and sinful natures?

Nearly every aspect of human behavior can be examined through an evolutionary lens.

Let’s start with why we began walking on two legs.

One theory, put forward by Kent State University professor Owen Lovejoy, who was part of the team that examined the famous Lucy fossil back in 1970’s, is that we needed our hands to carry stuff.

I love this theory because it includes committed couples as part of our evolutionary history, something I’m sure my Sunday School teacher would have appreciated.

Lovejoy proposes that early humans needed two hands to carry food and infants, and that females were attracted to males who were good at both carrying stuff and caring for the family.

Lovejoy points out that humans, unlike chimpanzees, don’t have huge, imposing incisor teeth to flash at rivals. Our teeth are small and nonthreatening, and that means males were not competing to acquire female ‘harems’, instead we pair-bonded and took care of each other.

Lovejoy and others believe that the defining evolutionary trait of humans is our ability to cooperate on a level not seen in any of our great ape cousins.

Evolution has taken many twists and turns on the way to Homo sapiens.

One early ancestor, Homo erectus, walked out of Africa and spread over most of Asia two million years ago.

This crafty brute is arguably the most successful human species, having conquered the world with little more than a thick brow ridge and a stone hatchet.

He may also have had fire, which is uniquely human.

Humans later hit a low point known as the ‘population bottleneck’ which is probably the defining moment in the evolution of our species.

According to a sophisticated genetic analysis, the entire human population 900,000 years ago shrunk to around 1,280 people of childbearing age.

That means you and me and all of the more than 8 billion people alive today are descended from what is essentially the population of the average high school scattered across Africa.

Around 500,000 years ago, our closest relatives the Neanderthals left Africa for the icy plains of Europe and Central Asia.

Modern Homo sapiens later met these tough and ancient people and for thousands of years we circled each other in a protracted deadly dance.

Today, every human outside of Africa has some Neanderthal DNA left over from that brief intermingling.

Neanderthals, unlike their brutish reputation, had complex emotional and spiritual lives, according to recent research.

Their downfall was that they just were not as good at working together in groups as we are.

Today, even as we slide into ever increasing factionalism, with war and bloodshed the dominant theme of human history since the fall from grace in the garden of Eden, our ability to work together has been our main evolutionary advantage.

What makes us human, according to evolution, is our ability to get along with each other.

I suppose when I asked the Sunday School teacher, "What about evolution," it presaged my career challenging authority as a journalist.

Embracing evolution was the first step in my lifelong passion for using science to explore what is often unknowable truths.