The usage of "actually"

The below is a test question asking the proper answer for the blank.

Can you try out?

Whereas general anthropology combines both nature and culture in its conceptual framework, social and cultural anthropologists are concerned with human beliefs and behavior that are not explicable in terms of biology. The basic assumption in sociocultural anthropology is that the range of variation in human belief and behavior cannot be explained by or reduced to biology. This does not mean that social and cultural anthropologists deny that biology has any influence on social life; to do so would be ridiculous. What it does mean is that they treat human biological make-up as a constant, and attempt to explain the range of social and cultural variation that is not reducible to biology. Actually, this merely confirms the importance of a fundamental principle of logic: ********, the constant in this case being biology.

? a constant cannot explain variation
? variation is converted into a constant
? sociocultural variation is nearly a constant
? variation is necessary to maintain a constant
? a constant exhibits a great deal of variation


The answer is #1. And that's OK with me. What I want to check out is the usage of "Actually." It seems little odd in its position.


By googling, I find out the source of the test statement. The test question has omitted the italicized two sentences. And the original shows why "Actually" was used by showing corresponding "not" in the prior sentence.

That lead me to the conclusion that if we want to make proper paragraph without omitted sentences, "Actually" should be altered to other connecting words, such as "In other words." Am I right?

(This original paragraph comes from Google Book Search. If there's any problem concerning copyright infringement. I'll cut out the below paragraph. But without it I cannot explain the problem properly.)

Whereas general anthropology combines both nature and culture in its conceptual framework, social and cultural anthropologists are concerned with human beliefs and behavior that are not explicable in terms of biology. The basic assumption in sociocultural anthropology is that the range of variation in human belief and behavior cannot be explained by or reduced to biology. This does not mean that social and cultural anthropologists deny that biology has any influence on social life; to do so would be ridiculous. What it does mean is that they treat human biological make-up as a constant, and attempt to explain the range of social and cultural variation that is not reducible to biology. We know that there are several types of family (for example, the nuclear family and the extended family), and several types of marriage (for example, monogamy, polyandry, and polygyny). The argument in socio-cultural anthropology is that such variation cannotbe explained by biology. Actually, this merely confirms the importance of a fundamental principle of logic:a constant cannot explain variation, the constant in this case being biology.