Learn Italian: Dieci anni fa, mio fratello ha scoperto un dente della preistoria. - Ten years ago, my brother discovered a tooth from prehistory.

Fa is actually the "it/he/she" form of the verb fare (to do/make). So, dieci anni fa literally means "it makes ten years". In Italian, when talking about time passed, fa always goes directly after the time period, just like "ago" does in English.

Why is it just mio fratello and not il mio fratello?

In Italian, you drop the definite article (like il or la) when using a possessive word with a singular, close family member. So it is mio fratello (my brother), but if the sentence were about multiple brothers, it would be plural and the article would come back: i miei fratelli.

Is scoperto an irregular past participle?

Yes! It comes from the verb scoprire (to discover). Since it is an -ire verb, you might expect the past participle to be "scoprito", but it is irregular. It follows the exact same pattern as aprire (to open), which becomes aperto.

Why use della (of the) instead of dalla (from the) for "from prehistory"?