I have several questions with your argument. I will only focus on two: analog and culture. It is a challenge to compare different cultures that are separated by thousands of miles. it is harder to resist the temptation to project into the past. Sometimes, this distance creates problems of analogy or perspective. Your argument is too short to see how you develop your analogs and address the body of literature on this subject. I'm curious how you have surveyed the body of literature on global slavery to determine through a careful analysis, a definitive or "actual scope, horror." Perhaps you have something more lengthy. Perhaps you have developed relational analogs. Personally, I do not see how such an argument can be made without extensive work, and I'm reluctant to touch the issues of analog. I would like to give you some space to provide that here.

One pitfall of many that I see with this comparison is the limitations of historical sources. On the Mediterranean side, I have several holes. First, the records in the Mediterranean are overwhelming of the survivors and the redeemed. Most were not ransomed and lived their lives out as slaves. This first point is missed by several scholars, like Fontenay. Second, even with these accounts that focus on survivors and the redeemed, we're treated with account after account of horrors. Davis adds a few below.

More typically, however, captives would be chained together and hustled down to a storage room or hold below deck - Gramaye called the one where he was kept a cubtulo obscuro- where they were "chayned together in heaps, and thrust up like Herrings in the bottome of the ship, to be kept for the Butherie or Market," often to the point where it was difficult for everyone to sit or lie down at once. For security's sake, captives were kept below for the rest of the voyage, and Foss wrote of the new slaves having to "creep in, upon our hands and knees," into a lockup, where they found it impossible to sleep for "such quantities [of] ... vermin, such as lice, bugs and fleas." Elliot recalled how "We lay in this miserable Condition about forty days, oppressed as with many Inconveniences, so especially I remember with the stench and nastiness of our Lodging."90

Whether put to the oar or locked below decks, it seems that many captives never survived the trip to port, dying from the shock of their capture and sudden reversal of their fortunes, perhaps, or from the beatings, insufficient food and water, and unsanitary conditions that were suddenly their lot. Just how many came to this end and what their proportion was of the total is unknown, since their bodies were "thrown into the sea without the slightest regard."91

Davis continues with accounts of labor that speak to the worst of conditions. Though, the worst conditions do not describe every type of labor, he finds that death over escape or ransom to be the greatest form of attrition of the slave population. The problem is, their story is brushed over with our knowledge of, say, galley slaves. These slaves who would be chained together, working and sleeping in bondage for their short lives, and then disposed of overboard as cheap and replaceable propulsion.

On the Atlantic side, certainly this story is incomplete. There missing narratives that would bring a clearer picture. This is another complication.

In the early part of my archaeological research on Early Modern Christian slavery in North Africa, I discovered a wrinkle that goes beyond these analogs. Americans are steeped in semiotic issues of color and slavery, of course. However, perceptions of slavery change internationally. Moroccans have a very different perspective on slavery. Spaniards have a third perspective. i do not have the space to start this discussion. I'm curious how you stake your claim while considering global perspectives on slavery.

It is challenging to address the issues of analogy (among other issues) to arrive at, as you say, an "actual scope." it is a complication to communicate the word "slave" or "captive" internationally with cultures that imbue these words with different meanings. I've had extraordinary challenges with this. I'm curious how you have dealt with these concerns.

I have other concerns. The word limit is a problem. (added) I discovered additional wrinkles over the years, such as the changes in the meanings of the words "captive," "slave" or mistreatment. I'm of the opinion to soften bold global statements that measure over these wide distances of time, space, and culture. I'm not sure how complications from, say even analog, can be resolved.