all dolphins in Shark Bay would go on to use ‘sponging’. Only around
one in ten have picked up the technique.[32] Why hasn’t the
behaviour spread further? Twenty years after biologists first
observed sponging, a group of researchers used genetic data to
show that the tactic was almost entirely the result of vertical
transmission. Dolphins are famously social, but it seems that after
one initial dolphin came up with the innovation, it only spread
through their family line. Individuals who weren’t related to them kept
on foraging sponge-free. In effect, this family of dolphins had created
their own unique tradition.
According to ecologist Lucy Aplin, both vertical and horizontal
transmission of culture can occur in the animal world. ‘It really
depends on the species, and also on the behaviour being learned.’
She points out that the type of transmission can affect how widely
new information spreads. ‘You might imagine in, say, dolphins, where
most of the learning happens vertically, you end up with family-
specific behaviours and it’s quite hard for behaviours to spread more
widely through the population.’ In contrast, horizontal transmission
can result in much faster adoption of innovations. Such transmission
is common in species of birds like great tits. ‘Much of their social
learning occurs horizontally,’ Aplin said, ‘with information gained by
observing unrelated individuals in the winter-flocking period, rather
than transmitted from parent to offspring.’[33]
For some animals, the difference between transmission types
could prove crucial to survival. As humans alter the natural
environment more and more, species that can efficiently transmit
innovations will be better placed to adjust to the changes. ‘Evidence
is increasingly showing that some species can show a high degree
of behavioural flexibility in the face of changing environments,’ Aplin
said. ‘As a result, they appear to be successful at coping with
human-modified habitats and human-induced change.’
Efficient transmission is also helping organisms resist human
change at the microscopic level. Several types of bacteria have
picked up mutations that make them resistant to antibiotics. As well
as spreading vertically when bacteria reproduce, these genetic