More black men are behind bars or under the watch of the criminal justice system than there were enslaved in 1850, according to the author of a book about racial discrimination and criminal justice.

Ohio State University law professor and civil rights activist Michelle Alexander highlighted the troubling statistic while speaking in front of an audience at the Pasadena Branch of the American Civil Liberties Union, Elev8 reports.

Alexander, the author of "The New Jim Crow: Mass Incarceration in the Age of Colorblindness," reportedly claimed there are more African American men in prison and jail, or on probation and parole, than were slaves before the start of the Civil War.

More than 846,000 black men were incarcerated in 2008, according to U.S. Bureau of Justice estimates reported by NewsOne. African Americans make up 13.6 percent of the U.S. population according to census data, but black men reportedly make up 40.2 percent of all prison inmates.

The criminal justice system is the newest in a long line of societal structures that have disenfranchised people of color, Alexander argues in her book, according to ColorLines.

In an excerpt from her book published on her website, Alexander writes that despite today's belief in "colorblindness," our criminal justice system effectively bars African American men from citizenship, treating them as a separate caste:

Denying African Americans citizenship was deemed essential to the formation of the original union. Hundreds of years later, America is still not an egalitarian democracy. The arguments and rationalizations that have been trotted out in support of racial exclusion and discrimination in its various forms have changed and evolved, but the outcome has remained largely the same.

More African American men were disenfranchised due to felony convictions in 2004 than in 1870, "the year the Fifteenth Amendment was ratified prohibiting laws that explicitly deny the right to vote on the basis of race," she wrote in a Huffington Post blog published last year.

Although crime rates have dipped in recent years, the number of African American men who are incarcerated has surged, mainly due to a single law enforcement policy, Alexander contends.

"Most of that increase is due to the War on Drugs, a war waged almost exclusively in poor communities of color," she said in the Pasadena lecture, according to LA Progressive.

That crime-fighting measure "is a big part of the reason that a black child born today is less likely to be raised by both parents than a black child born during slavery," she wrote in a 2010 Huffington Post blog.