比較級の文です。時制の違いについて教えてください。

ジェンダーに関連する文化的差異についての記述です。

Early human males were about twice the size of females, just as males are today
among such species as gorillas and orangutans, which are related to humans.
In the course of human evolution, however, the biological differences between the
two sexes were radically reduced.

Thus, apart from differences directly related to reproduction, whatever biological basis
there once was for gender role differences has largely disappeared.

Nevertheless, cultures have maintained some distinctions of gender roles ever since,
although these are far greater in some societies than in others.
Strangely enough, gender differences were more extreme in late 19th and early 20th
century Western societies, where women were expected to submit completely to male
authority, than they are among most historically known pre-agricultural peoples
whose ways of life resemble those of the late Stone Age ancestors of Western peoples.

下から２行目、than の後ろ
過去形でなく、they are と現在時制なのはどうしてですか？

よろしくお願いします。

No.1 ベストアンサー 回答者： wind-sky-wind 回答日時： 2018/01/03 22:44

than の前は19世紀末から20世紀初めの西洋社会の

性差（過去のこと）
それと比較する than 以下は現在の、先農耕民族の性差
（彼らの生活様式は西洋民族の祖先の生活様式に似ている）

この回答へのお礼

>現在の、先農耕民族の性差

読み間違えていました。。
ありがとうございました！

お礼日時：2018/01/03 23:12