A population of 200,000 Hottentots in the Cape was reduced to just 32,000 (under the Dutch) "through a continued system of oppression".
The Colonial Records of 1663 refer to infectious diseases killing a large number of Hottentots - further outbreaks of smallpox followed in 1713 and 1755.
Extracts from a letter by Lieutenant Governor Andries Stockenstrom dd 31st December 1830 to the inquiry:
Exactly in the same way as the boers gradually encroached on the aborigines within the present boundaries of the Colony, but with a great deal more cruelty, because they were more irresponsible, the Griquas did beyond said limits. By the time the former intruders reached the branch of the Orange River now called Swart or Cradock River, the latter had secured possession of the country as far eastward as Ramah and the lower parts of the Mud and Vaal Rivers . The disputes between the Griquas, among themselves, caused one party to fly higher up the Mud River branches and there provisionally settle under the name of Bergenaars. Philippolis (named after Dr Philip of the London Missionary Society) continued to be exclusively a Bushman Missionary Establishment as late as 1827; the country in every direction beyond it for a vast extent, no one presumed to consider as belonging to any other but that people, though the Colonialists as well as the Griquas coveted it and migrated into it from time to time until the Griqua Chief, Adam Kok, and his party, at length fixed permanent residence in those parts contiguous to said branch of the Orange River, including Philippolis.
(The territory around Philippolis was ceded to the Griquas and Dam Kok by Dr Philip in the name of the London Missionary Society).
But instead of protecting the natives, the Bushmen, the Griquas behaved to them in a most brutal manner. In a short time not a single Bushman remained at the Institution of Philippolis, expressly established for them, or anywhere near. Upon the slightest provocation the were shot like wild beasts, and the lands and springs they were dispossessed with much more violence and less ceremony than the boers had dared to do in the worst of times.
The acts are it is the Bushman country which the boers and Griquas are seizing; these savages are too weak to resist either of these intruding parties, and without some interference, they will there give away (sic), and disappear, as they have on every other part of South Africa, as it gradually became occupied by a stronger and more civilized people.
until the Griquas came and made the Bushman country "their own country" saying that they were authorised to do so by Dr Philip, at the same time arrogating to themselves the right to preventing the migration f the boers into the Bushmen country.
By 1834 there were about 1,500 boers on the other side of the Orange River and for the most part in the Griqua country. Of these there were 700 boers for several months during the year in the district of Philippolis alone with at least 700,000 sheep, cattle and horses.
Besides destroying the pastures of this people, in many instances their corn fields were destroyed by them and in some cases they took possession of their houses.
More on Stockenstrom's biography at this link
Dr Philips on Hendrick Hendricks:
"He (the chief Kok) is entirely under the influence of Hendrick Hendricks, his son-in-law, who is one of the leading men among the Bergenaars and the worst and most dangerous man among that party. Hendricks is clever and he is plausible but he is a thorough scoundrel and such is his power over the old chief (Adam Kok) that whatever resolution he may form and whatever declaration he may make concerning it, in half an hour Hendrick can make him change his mind.
At a single stroke of the unscrupulous pen of the representative of the London Missionary Society (Dr Philip) contributed to from the highest and best of motives by many of the most enlightened, religious and humane community in the world, to Adam Kok's own plundering and murderous Bergenaars are, for the protection of the Bushmen ! converted into Griquas and the Bushman territory into the "Griquas' own country".
(The "Griqua" Bergenaars under Hendrick Hendricks ruthlessly exterminated the Bushmen in this territory)