The modern theory of evolution does not require gradual change. A new species can arise when a small segment of the ancestral population is isolated at the periphery of the ancestral range. Large, stable central populations exert a strong homogenizing influence. New and favorable mutations are diluted by the sheer bulk of the population through which they must spread. They may build slowly in frequency, but changing environments usually cancel their selective value long before they reach fixation. But small, peripherally isolated groups are cut off from their parental stock. They live as tiny populations in geographic corners of the ancestral range. Small peripheral isolates are a laboratory of evolutionary change.

—STEPHEN JAY GOULD, "THE EPISODIC NATURE OF EVOLUTIONARY CHANGE," THE PANDA'S THUMB: REFLECTIONS IN NATURAL HISTORY, 1980

Chapter 20

Urquhart Bay, Loch Ness

The research vessel, Nothosaur, drifted in 730 feet of water, adding to the picturesque backdrop of Urquhart Castle. The banks of the ruins were lined with tourists, the scene recorded by a half dozen TV camera crews, the footage destined to be used in news reports around the globe as B-role.

Michael Hoagland remained on deck to shout imaginary orders to his crew until the last camera was finally lowered, then he hurried inside to the control room and the ship's sonar system.

* * *

Sonar systems function by emitting ultrasonic pulses from an acoustic projector. Hydrophones then analyze these reflected signals to determine if an obstacle or object is present within the field.

There are two basic types of sonar: passive and active. Passive sonar, used aboard submarines, analyzes incoming noises without creating its own sounds so as not to give away the vessel's location. Active sonar emits loud "pings" that can be set at different frequencies, bearings, or angles. Pings travel at a speed of approximately fifteen hundred meters per second. If an object lies in the beam's path, it will be detected on echo-ranging sonar.

While more aggressive, the limitation of active sonar is that it takes time to adjust the projector, emit a ping, and listen for an echo. To combat this challenge, engineers developed the sonar buoy, a free- floating unit that emits its own system of pings, allowing operators to detect objects moving through its acoustical field.

The Portable Acoustic Measurement System, known as PAMS, consists of an array of sonar buoys, distributed along the surface in a preset pattern. PAMS signals are linked to an acoustic data acquisition system, a GPS receiver, and a radio telemetry sub system. Positional data is then transmitted by way of a UHF radio link to the analysis station where signals are evaluated.

* * *

Over the last nine hours, the Nothosaur's crew had deployed sonar buoys every two kilometers, beginning in the waters off Fort Augustus. Consisting of two parallel rows, the array ran north to Tor Point, where the Loch's width narrowed and the field was reduced to a single row of buoys which concluded at Lochend and the Bona Narrows.