There is another way though—a way for modern medicine to make use of modern technology rather than the blood of an ancient animal. A synthetic substitute for horseshoe-crab blood has been available for 15 years. This is a story about how scientists quietly managed to outdo millions of years of evolution, and why it has taken the rest of the world so long to catch up.So reliant is the modern biomedical industry on this blood that the disappearance of horseshoe crabs would instantly cripple it. And in recent years, horseshoe crabs, particularly in Asia, have come under a number of threats: habitat loss as seawalls replace the beaches where they spawn, pollution, overfishing for use as food and bait. Horseshoe crabs bled for the biomedical use in the United States are returned to the ocean, but an estimated 50,000 also die in the process every year.