Yeast doesn't live *only* at 37 degrees Celsius. That's actually the optimal temperature for many *human* cells, like those in our bodies. Yeast, on the other hand, can thrive in a wider range of temperatures.

Here's a breakdown of yeast and temperature:

* Optimal Temperature: Most common yeast strains used in baking and brewing, like *Saccharomyces cerevisiae*, have an optimal temperature range between 25°C and 30°C (77°F - 86°F). This is where they are most active, converting sugar into alcohol and carbon dioxide.

* Tolerance: They can survive and even reproduce at temperatures between 5°C and 40°C (41°F - 104°F), although their activity will be slower at the colder end of this range.

* Extremes: There are some yeast species that can tolerate much higher or lower temperatures, but they're not as commonly used.

Why 37°C is not ideal for yeast:

* Human Body Temperature: 37°C is our normal body temperature, and many human pathogens thrive at that temperature. Yeast, however, aren't generally considered pathogens in the same way.

* Higher Temperatures: Temperatures above the optimal range can actually slow down or even kill yeast. Think about how bread dough rises more slowly in a warm kitchen vs. a cooler one.

In short, yeast can live in a variety of temperatures, but they are happiest and most active in a range below the human body temperature.