The Pulse explores how the environment shapes biology. Turns out that influence goes deep, down to the molecular level — to the DNA of humans and animals.

Also heard on this week’s show:

As drug overdose deaths continue to soar, cities hit hard by the opioid crisis are considering a controversial new proposal: safe injection sites. That’s where people can bring their illicit drugs — and inject them — under medical supervision. Supporters say this harm-reduction approach saves lives.

For more than a decade, Vancouver has been experimenting with safe injection sites. On this episode, we travel there to talk with users, staff, advocates, and neighbors, and see what lessons the city has for communities hoping to curb drug deaths.

Also heard this week:

Rebroadcast: Happy Birthday, America! From the very beginning, science has shaped this country. Many of the Founding Fathers — Madison, Jefferson, Washington — were science geeks, and their methodical way of thinking is reflected in the Declaration of Independence.

To celebrate the holiday, we dig into the science that makes fireworks sparkle, flags durable, and hot dogs delicious. Plus, what brain researchers are learning about the pursuit of happiness and feelings of patriotism.

The Atlantic hurricane season is here — that time of the year when tropical storms whip their way in from the sea, cutting paths of destruction from Nova Scotia all the way down to the Caribbean. From Katrina back in 2005, to Harvey and Maria more recently, we’ve seen the devastation these storms can do. How do we prepare better — and recover more fully? In this episode, we hear stories about the power of hurricanes, and how we deal with them.

Also heard on this week’s episode:

We have dogs to thank for pacemakers. We probably should be a little grateful to mice for the development of chemotherapy. Cows helped us conquer smallpox, and chimp research led to the new ebola vaccine. But despite those breakthroughs, animal testing makes a lot of us squirm. On this episode of The Pulse, we explore our complicated relationship with lab animals (and insects). How do we treat them? What are we learning? And what do we owe them?

Also heard this week:

On this week’s show, we talk with people taking their health and wellness into their own hands — with varying results.

A gun can change a moment, a life, a family, an entire neighborhood. Like a catalyst in a chemical reaction, guns have a unique ability to transform the calculus of a situation. A gun can make you feel safe. Sometimes it’s symbol of cultural identity. It also has the power to destroy. On this episode of The Pulse, we look at the difference a gun makes.

Also heard on this week’s episode:

We like to romanticize farming – but the truth is that it’s tough, complicated, sometimes dangerous work. Technology has made some of that work easier, but it’s also brought a whole new set of pressures. In today’s episode, we hear about what some people are doing to help save America’s family farms.

Also heard on this week’s show:

Giving birth. Giving support and feeling a fierce love. Being there. Being exhausted. It’s all part of being a mom. To mark Mother’s Day, we’ll reflect on some of the ways humans and other species juggle the never-ending demands that come with mothering. We’ll meet scientist moms who balance taking care of kids and applying for research grants. We’ll find out how America’s OB GYN shortage is affecting women in rural areas. We’ll observe the bird who wins the award for worst mother ever, or maybe she’s the smartest? Plus, we’ll talk about the “mother of all science”.

When it comes to scientific knowledge, we’re selective about who and what we believe. But, how do we get to a place of knowing? We hear from people who were believed — and those who weren’t — to find out what made the difference.

Also heard on this week’s show: