before主句的时态可以是目前完成时吗

老师好！向老师请教一个句子：

Though they’ve been around long beforewe walked on the earth, sharks still attract us to this day.

请问：they’ve been aroundlong before we walked on the earth 中的have been around 的时态是不是合理，是不是应改为hadbeen around？

作者偷了一个懒，句子省略了一个since介词短语：

Though they’ve been around since a time long before we walked on the earth, sharks still attract us to this day.

long before we walked on the earth是修饰time的定语，目前完成时表示自从人类出现以前很长时间一直到目前，鲨鱼都是存在的。