If we define diversity as any and all differences between and among people, we immediately face the challenge of figuring out which differences are at play as well as which are significant. One approach to this challenge is to try to identify types or categories of difference. For example, scientists deal with the tremendous diversity in the natural world by classifying plants and animals into groups that share physical characteristics and giving these groups names, such as birds and mammals, reptiles and amphibians.
Historically, scientists described human diversity largely in terms of physical differences – sex and “race” being the main categories. We know that sex is an important type of biological diversity, though as we saw in Module 1 it cannot be reduced to male and female. In Module 2, we saw that sex is linked to gender – the social ideas and assumptions about what it means to be male or female in a given place at a given time. Gender is an important category of human diversity because it affects almost every dimension of our lives. So, when thinking about human diversity, it is important to think about the continuum of sex and gender.
The category of race is more similar to the concept of gender than sex. Although people often talk about different races in the human population, researchers in many fields have come to the conclusion that race as a biological category does not exist. Like gender, race is a social and historical idea, rather than a biological reality. This is not to suggest that there aren’t visible differences in the human population that can be grouped into categories. People of African descent tend to look different than people of Anglo-Saxon descent. But it is not the visible differences themselves that affect well-being, but rather our reactions to these differences. In other words, race as a biological category may not exist, but racism certainly does and people suffer in many ways as a result of stigma and discrimination. 
“Ethnicity” is a more acceptable term than “race” in many parts of the world and it may be helpful in encouraging us to look beyond physical variation to consider diversity in heritage, culture, language, experiences, etc. For example, African Canadians often share physical characteristics that lead others to label them as a single group or race. But African Canadians are a diverse group: they come from different parts of the world with different histories, cultures, and traditions; some wear jeans and some wear robes; some of them have lived in Canada for generations while some immigrated fifty years ago and others arrived more recently; some of them speak only English or French while others speak several languages.
Whether we decide to use the term race or the term ethnicity to describe specific visible differences, it is important to remember that social rather than biological factors are what make this type of diversity powerful. It is equally important to remember that there is a great deal of variation among and between people who seem to look the same as well as many similarities between and among people who look different.
In addition to sex and gender, and race/ethnicity, there is a host of other types of diversity: income, education, employment, sexual orientation, safety, housing, food security, family structure, disability, etc. Many of these differences affect large groups of people in Canada. For example, in 2006 close to 4.5 million people in Canada were living with a disability. In the same year, 16% of families in Canada were headed by a lone parent – most of them women. In 2007-2008, 7.7% of households in Canada, or almost 956,000 households, experienced food insecurity.
Differences affecting small groups of people are also important. Only a small proportion of people in Canada identify themselves as gay, lesbian or bisexual, but they are far more likely than heterosexuals to encounter stigma and discrimination. Even if they don’t experience direct discrimination, they live in societies that often don’t acknowledge their existence – as in television programming and health services – or don’t reflect their values, language and experiences. These types of diversity are profoundly important yet often invisible in research, policy and practice. 
Every dimension of diversity has the potential to influence people’s needs, experiences, and opportunities and therefore must be acknowledged and taken seriously.
Sources:  Guido Barbujani (2005). Human races: Classifying people vs understanding diversity. Current Genomics, 6 (4): 1-12: http://www2.webmatic.it/workO/s/113/pr-465-file_it-Current%20Genomics%204.pdf;  Disability rates by sex and age groups, Canada, 2006, http://www.statcan.gc.ca/pub/89-628-x/2007003/t/4183086-eng.htm; Distribution of census families by family structure, census metropolitan areas, 2006, http://www12.statcan.gc.ca/census-recensement/2006/as-sa/97-553/table/t11-eng.cfm; Household food insecurity, 2007–2008, Canadian Community Health Survey, http://www.statcan.gc.ca/pub/82-625-x/2010001/article/11162-eng.htm