Why were slaves not considered to be people?

The concept that all human beings are born with fundamental rights we're not prevalent in the 1700s. if you were born at the bottom of society, you live the life of poverty and hard work and toil. other people would be own just like goods and money. this was a view of humanity that made life hard for servants all over the world. and not least for the enslaved laborers that worked inhumane conditions.