They were fusions which are evolutionarily programmed for.是什么意思？

They were fusions which are evolutionarily programmed for.

它们是进化上已安排好的融合现象.

they

pron. 他/她/它们，人们，大家，政府，当局，她们；

例句
The storms had abated by the time they rounded Cape Horn.
他们绕过合恩角时，暴风雨已经减弱。

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

fusions

n. 熔合( fusion的名词复数 )，核聚变，联合，合并；

例句
His previous fusions of jazz, pop and African melodies have proved highly successful.
事实证明他先前融合了爵士乐、流行乐和非洲旋律的作品非常成功。

which

pron. 哪一个，哪一些，哪个，那，指前面提到的事物；adj. 哪一个，哪一些；

例句
...the latest date at which a foetus can be aborted.
能够打胎的最迟日期

are

vi. （用于第二人称单复数现在时，第一、三人称复数现在时）是；n. 公亩（等于100平方米）；

例句
We are scared to abandon ourselves to our feelings in case we seem weak or out of control.
我们不敢放纵自己的情感，以免显得太过软弱或缺乏自制。

programmed

v. 训练( programme的过去式和过去分词 )，培养，预调；

例句
He programmed his computer to compare all the possible combinations.
他给他的计算机编制了一套程序，以比较所有可能的组合。

for

prep. 为，为了，倾向于，关于，当作；conj. 因为，由于；

例句
I've come looking for a bit of advice.
我特来讨教。