From: veritasium
Overview
Snake venom is a complex biological weapon that evolved from saliva, primarily used for catching and digesting prey [00:03:20]. Each snake species possesses a unique venom tailored to the specific animals it hunts [00:03:25]. The venom gland itself is situated behind the snake’s eye [00:03:42].
Evolutionary Development of Fangs
Originally, venom was delivered into a snake’s mouth by its back teeth [00:03:31]. To this day, approximately two-thirds of all snake species are rear-fanged [00:03:37].
Over time, evolutionary pressures led to the fangs moving closer to the front of the jaw in some species, enhancing the snake’s ability to capture and kill prey [00:03:55]. Concurrently, the fangs themselves evolved:
- Smooth Teeth: Fangs began as ordinary, smooth teeth with venom flowing down the outside [00:04:09].
- Grooved Fangs: Some snake lineages developed a groove in each fang to channel the venom flow [00:04:16].
- Hollow Fangs: In certain species, this groove deepened and eventually closed to form a hollow tube, allowing the teeth to literally inject venom into prey [00:04:21].
However, hollow fangs are not the norm, existing in only about one-seventh of the world’s snakes [00:04:32]. In Australia, almost all venomous snakes possess hollow fangs [00:04:37].
Potency and Composition of Venom
The Australian Reptile Park actively breeds snakes to produce more venom than their wild counterparts through selective breeding [00:05:14]. For instance, some coastal taipans bred at the park produce five to seven times the venom of their wild relatives [00:05:20]. A scratch from these highly venomous animals can be lethal [00:05:44].
The concept of the “most venomous snake” is complex because venom evolves for potency against specific prey [00:08:00]. Prey animals, in turn, can evolve resistance to venom; for example, the honey badger is almost completely immune to Cobra venom [00:08:08]. The lethality of a bite depends on the snake species, the bitten animal, and the amount of venom injected [00:08:16].
A 1979 study tested the venoms of 25 different snake species on lab mice to estimate the required antivenom dose [00:06:19]. Based on this, a single King Cobra bite could kill approximately 13,000 mice or around four human-sized rodents [00:06:14]. The inland taipan, found in Australia, is considered the most venomous snake globally by this measure, with one bite containing enough venom to kill half a million mice or over 100 humans [00:06:41].
Types of Venom Effects
Snake venoms typically contain up to 200 compounds [00:09:44]. These venoms are lethal because they target molecular pathways that are conserved across vertebrates and even the entire tree of life [00:08:53]. The four main ways snake venom can kill include:
- Neurotoxic: Damages the nervous system and brain by interfering with neurotransmitters [00:09:10].
- Hemotoxic: Thins blood, preventing wounds from healing and causing internal bleeding by disrupting blood coagulation [00:09:19].
- Cytotoxic: Attacks cells, leading to severe blisters, necrosis, and cell death [00:09:30].
- Myotoxic: Destroys muscles and causes paralysis [00:09:37].
Most venoms contain a combination of these neurotoxic, hemotoxic, cytotoxic, and myotoxic proteins, making snake bites challenging to treat as dozens of toxins work together [00:09:47].
Human Susceptibility
Humans are particularly susceptible to snake venom because we are closely related to their main prey, rodents [00:08:33]. Rodents and primates diverged on the evolutionary tree only about 75 million years ago, leading to shared biology, including cell structure, blood clotting mechanisms, and nerve signaling [00:08:39].