A dog that dominated the world for 2 million years became extinct because of its picky eating habits

When it comes to the oldest of the Canidae, many people think of the wolf. The wolf is relatively large, carnivorous, and has a wide distribution range, mainly in Eurasia and North America, from south to north.

Image source: veer gallery

Although wolves are now widely distributed in nature, their origin is relatively recent. Wolves originated in Eurasia 400,000 years ago and entered North America in the late Pleistocene (130,000-11,000 years ago). In contrast, the human genus has appeared for more than 2 million years, and the ancestors of tigers appeared in North China as early as 2.5 million years ago.

Before the rise of wolves, who dominated the dog subtribe? How did its survival strategy differ from that of wolves?

Part 1

It was the leader of the canine family 2.5 million years ago.

In today's Caninidae, in addition to the genus Canis, there are three evolutionary lineages. The first is the two jackals on the African grasslands, namely the side-striped jackal (Lupulella adusta) and the black-backed jackal (Lupulella mesomelas); the second is the African wild dog (Lycaon pictus) on the African grasslands, as well as the jackal (Cuon alpinus) in South Asia, Southeast Asia and East Asia.
Going back in time, the animal most likely to dominate the Canidae family among these branches would have been the prehistoric relative of the African wild dog, the Xenocyon.

Xenocyon antonii is a representative of Xenocyon antonii in East Asia and Xenocyon falconeri in Europe.

The fossil of the jackal (discovered in Jinyuan Cave, Luotuo Mountain, Dalian, 500,000 years ago) and the African wild dog (living specimen)

(Image source: Reference 1)

They were large, had sharp teeth, and were similar in size to today's wolves (40-50 kg), occupying a very similar ecological niche. In the middle of the Early Pleistocene (~1.8 million years ago), this lineage entered Africa and evolved into the genus Lycaon.

During the same period, early members of the genus Canis had also spread widely across Eurasia, but the individuals of the Canis species of this period were generally smaller, similar to today's coyotes in North America, and would not hunt large prey in groups like today's wolves.

African wild dog (Photo source: veer photo gallery)

During the long Early Pleistocene, the Eurasian jackals further expanded their territory, entering South Asia around 1.4 million years ago, and then entering the Southeast Asian islands around 1.1 million years ago. Since no jackals have been found in southern China, it can be inferred that the Southeast Asian jackals migrated from South Asia.

Subsequently, the island regions of Southeast Asia were isolated due to rising sea levels, and the Xenocyon living there gradually shrank in size to become Xenocyon trinilensis, whose individual size is equivalent to that of today's jackals (15-20kg).

The lineage of the Xenocyon in Europe exchanged genes with the ancestors of the jackals and evolved into the island jackals (Cynotherium) on the islands of the Mediterranean. After entering the Middle Pleistocene (780,000 years ago), the Xenocyon further expanded its sphere of influence and entered North America through the Bering Land Bridge, where it evolved into the Texas Xenocyon (Xenocyon texanus), which flourished for a time.

In contrast, the canines that are now so powerful, especially wolves, remained smaller in size during the Early Pleistocene to the Early Middle Pleistocene, mainly represented by the Mosbacher wolf (Canis mosbachensis). The Mosbacher wolf was the most numerous canid in the Zhoukoudian Homo erectus site.

The individual size of this wolf is similar to that of today's coyotes, and its habits may also be similar. It mainly acts alone or in small groups and preys on small and medium-sized prey, which is different from today's wolves.

The alligator became extinct about 500,000 years ago, while the earliest wolves appeared in northern Eurasia around 400,000 years ago and quickly became an important part of the ecosystem, and have thrived to this day.

Mexican Gray Wolf

(Photo source: veer photo gallery)

This shows that the now famous wolves did not always live in the vast grasslands. For most of the Pleistocene (2.5-500,000 years ago), the Alien Jackal family was the leader among canids. It was not until the Alien Jackal became extinct about 500,000 years ago that Canis seized the opportunity and eventually evolved into a powerful species like wolves, replacing the Alien Jackal.

Part 2

The decline of the Jackal Empire: It was actually because of picky eating

How did the once invincible alien jackal become extinct?

In fact, although both Canis and Alien Jackals are considered large predators, Alien Jackals are generally larger and more marginal in distribution. Therefore, Alien Jackals are considered "big guys" in most areas of their distribution range. In addition, the teeth of members of the African wild dog-Alien Jackal family are relatively sharp, which is a characteristic of carnivores, and they are not very good at eating plants.

Migration map of the African wild dog-jackal family

(Image source: Reference 1)

In contrast, the size of Canis is more diverse, with members of the family ranging from medium-sized animals such as the Asian jackal, which weighs only about 10 kg, to large animals such as wolves. In terms of diet, Canis species are not as monotonous as the exotic jackal. For example, the diet of the Asian jackal contains more plant-based foods, while wolves, although they mainly feed on meat, occasionally eat plant-based foods.

Therefore, we can see that canines have a wider range of adaptability than the jackals. After the Earth experienced the Middle Pleistocene Revolution, the fluctuation range of global climate gradually increased, and the instability of climate further increased. Many "old-fashioned" carnivores, such as the saber-toothed tiger family's saw-toothed tiger, the giant chin tiger, the huge hyena member of the hyena family, and the giant cheetah that dominated the Early Pleistocene, became extinct or declined during this period.

The common feature of these species is that they have a relatively simple diet and can only survive by relying on larger prey. The jackal did not escape the torrent of climate change and disappeared in the long river of history, while the Canis family seized the opportunity, rapidly grew in size, and eventually became the new masters of the grasslands in the Northern Hemisphere.
The succession of the genus Canis and the genus Alien Jackal reveals to us that no species can thrive forever. If a species takes a different path in the process of evolution, it is easy to become extinct when the climate and environment change.

References:

1. Jiangzuo, Q., Wang, Y., Song, Y., Liu, S., Jin, C., Liu, J., 2022. Middle Pleistocene Xenocyon lycaonoides Kretzoi, 1938 in northeastern China and the evolution of Xenocyon-Lycaon lineage. Historical Biology, 1-13.

2. Rook, L., 1994. The Plio-Pleistocene Old World Canis (Xenocyon) ex gr. falconeri. Bollettino Della Societa Paleontologica Italiana 33, 71-82.

3. Tedford, RH, Wang, X., Taylor, BE, 2009. Phylogenetic systematics of the north american fossil caninae (Carnivora: Canidae). Bulletin of the American Museum of Natural History 325, 1-218.

4. van der Geer, AAE, Lyras, GA, Volmer, R., 2018. Insular dwarfism in canids on Java (Indonesia) and its implication for the environment of Homo erectus during the Early and earliest Middle Pleistocene. Palaeogeography, Palaeoclimatology, Palaeoecology 507, 168-179.

5. Wang,

6. Jiang Zuoqigao, 2021. Geological distribution of large canid species in the Pleistocene of China: current status and prospects. Chinese Science Bulletin 66, 1426-1440.

Produced by: Science Popularization China

Produced by: Jiang Zuoqigao

Producer: Computer Network Information Center, Chinese Academy of Sciences

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