On August 23, UNESCO marks the sombre “International Day for the Remembrance of the Slave Trade and its Abolition.”

The Slave Trade referred to in UNESCO’s proclamation is the so-called Atlantic slave trade, in which more than 12 million men, women, and children were wrenched from their homes in Africa to toil in the fields of the United States, the Caribbean, and elsewhere.

In her 2014 message, UNESCO’s Director General, Irina Bokova, says that, “transmission of this history is an essential condition for any lasting peace based on mutual understanding among peoples and full awareness of the dangers of racism and prejudice.” That may be true, but recent events in Ferguson, Missouri suggest we have a long way to go to achieve this.

It’s tempting to believe that humankind has matured from the thinking that allowed centuries of sickening slavery to take place. Yet today there are an estimated 20 million people enslaved in the world. To put that number in context: It’s more than half the population of Canada. Modern slavery may not involved the wholesale, state-sponsored barbarousness of the Atlantic slave trade, but for those enslaved, the distinction doesn’t much matter.

Slavery neither began nor ended with the Atlantic slave trade. The practice of enslavement is as old as human civilization. For example, almost 4000 years ago in Mesopotamia, the cradle of Western Civilization, the ruler Hammurabi set out laws regarding slaves. Slaves were used in Egypt to build the pyramids, and also in China to build the Great Wall.

The Roman Empire at its height included an estimated 12 million slaves. At times, one-quarter of the empire’s population were slaves. The rise of Christianity and Islam did not end slavery, but shifted the dynamics. Slavery remained a fact of life, but slaves could not be made of those from the same faith. During the Middle Ages, millions of slaves were traded both ways across the Mediterranean.

Even before the Americas were colonized, slaves were abducted from Africa to labour in Egypt, Arabia, and beyond. Once the plantations of North and South America were established, the trade routes flowed west instead of east. For over 300 years, the insatiable need for labourers in the Americas resulted in an appalling period of history. It is painful to realize that slavery in the Americas only ended, officially at least, around 150 years ago in 1863-1865. (The trade in slaves was abolished earlier by Britain and the United States in 1807; other countries followed their example over the next decades. However, ending the trade did not end slavery in those countries?that came later.)

Today, slavery and slave trading are illegal in every country of the world. Despite slavery’s illegality, however, the United Nations estimates that 20 million people?the Global Slave Index says closer to 30 million?are enslaved worldwide. Almost half of those are children. According to UNESCO’s website, “while the means through which modern and traditional forms of slavery have operated differ greatly, the violation of human rights and human dignity are central issues in both practices.”

Modern slavery is often referred to as “human trafficking,” which the UN defines as “the recruitment, transportation, transfer, harbouring or receipt of persons, by means of threat or use of force or other forms of coercion, of abduction, of fraud, of deception, of the abuse of power or of a position of vulnerability or of the giving or receiving of payments or benefits to achieve the consent of a person having control over another person, for the purpose of exploitation.”

The existence of slavery and the trade of slaves?a.k.a. human trafficking?continues. Sadly, humankind appears not to have matured to the extent we would wish. Philosopher and poet George Santayana (1863-1952) observed that “those who forget history are doomed to repeat it.” On August 23, let us remember this history.

You can find more information about the “International Day For the Remembrance of the Slave Trade and its Abolition” on UNESCO’s website. Enlightening statistics on modern slavery appear on Global Slavery Index‘s website. You can also follow the conversation on the United Nation’s “Remember Slavery” pages on Facebook and Twitter.

Barbara Lehtiniemi is a writer, photographer, and AU student. She lives on a windswept rural road in Eastern Ontario