Trans-racialism
Often posed as a hypothetical to argue by contradiction by comparing being transgender to being trans-racial (identifying as a different race), trans-age (identifying as a different age) or trans-species (identifying as a different species or animal.) Some examples given are Rachel Dolezal and Oli London.
In short, gender identity is personal to the individual who has that identity (it is not inherited) whereas race is also defined by culture and ancestry.
The difference between categories
This pre-supposes that gender, race, age and species are all objective and factual classifiers that must all be self-identified or none must be self-identified. However, these classification systems are not all the same. This may also be a form of essentialism that insists that people of different genders or races are entirely separate, mutually exclusive, “things”.
Gender and race are complex sociological parts of our identity. Neither gender1 nor race2 is based on biology. This doesn’t mean they’re not real. However, they are primarily social constructs. Transgender identity has been widely studied, validated and been incorporated into guidelines for medical and healthcare organizations3. Transracial identities have caused considerable controversy4 due to the fact that as a construct, race is largely based on your parents and the culture and place you grew up in.
Age and species are also constructs, but have more objective definitions: the years since birth, and a taxonomic classification.
More information
Gender, race5, age and species are all at least partly socially constructed, that is, they are labels that people put on top of real phenomena in order to help understand, categorize, or judge things. But not all constructs are equal: because their definitions vary (see Social construct.)
They can also be more or less fluid in how their definitions change over time based on updated understanding, and so on. In the case of race, the move away from being primarily defined by biology (as was the case with scientific racism) happened in the later half of the 20th century. Race is generally self-identified, and is generally expected to be a combination of one’s ancestry, culture, and physical qualities. It can also be fluid. The perception of one’s racial identity can shift with experience and time6.