Animals that became extinct long ago can be understood thanks to which resource?

fossils, and the people that make discoveries based on these fossils

Explanation:

The given line meant that the desire to get gold led to frenzied arrival and interest in people. People want gold and it was even felt on the East Coast despite the gold discovery was on the West Coast.

Explanation:

The start of the Gold Rush began with the discovery of gold nuggets in the Sacramento valley in 1848. This resulted in the arrival of many gold miners to the area. And as more and more gold was discovered, people began to arrive in thousands with the prospect of discovering gold for themselves.

When the news of the gold discovery reached the East Coast, it led to massive interest and want of gold. It also led to the rise in the importance and significance of gold, leading to 'gold fever'. The term "gold fever" is used to refer to the frenzy of wanting and desiring gold by people. And with the frenzy spreading even to the East Coast, it led to a massive surge in the interest to get gold. And so, people in the East Coast also entered the 'race' to discover gold for themselves. It means that the interest and desire to get gold has reached to even the East Coast.